摘要:

86 PTCKERINQ THE DETERGENT ACTION OF SOAP. X.- The Detergent A ction of Soap. By SPENCER UMFREVILLE PICKERING. ALTHOUGH the detergent action of soap is much increased by the presence of excess of alkali it exists independently of such excess, and cannot be attributed to the alkali liberated by hydrolysis, since that would imply a reversal of the action liberating it. Hillyer ( J . Amer. Chem. Soc. 1903 25 511) considers that the cleansing action of soap “ i s largely or entirely t o be explained by the power which it has of emulsifying oily substances of wetting and penetrating into oily textures and of lubricating textures and impurities so that they may be removed easily and it is thought that all these properties may be explained by taking into account the low cohesion of soap solutions and their strong attrac-tion adhesion or affinity to oily matter which together cause the low gurf ace tension between soap solutions and oil.” Although low surface tension cannot n o y be accepted as an explanation of emulsification emulsification is certainly an important factor in the detergent action of soap for emulsified globules are surrounded by a pellicle which prevents them from wetting and rendering oily any solid matter present.Spring (Bull. Acad. Roy. Belg. 1909 lS7 1128) considered Hillyer’s explanation insufficient’ and showed that dirt as exemplified by lamp black silicic acid clay and cellulose combines with the acid soap resulting from hydrolysis t o form colloidal absorption compounds and in some cases increases the amount of acid soap formed.It is doubtful however how far this action is of practical importance f o r i t could not occur if excess of alkali sufficient to’ prevent hydrolysis were present yet the deter-gent action is actually increased by such excess. A factor which neither of these investigators appears t o have recognised is probably the most important of all namely that oils are actually soluble i n soap and to a very large extent; even paraffin oil will dissolve in quantities up to 100 per cent. of the soap present. This solubility is probably not altogether unknown to soap manufacturers for it was certain observat,ions communi-cated by a manufacturer which led the author t o examine the matter; yet H. H. Cousins who investigated the subject (“The Chemistry of the Garden,” 1916 p.132) appears to have con-cluded erroneously that paraffin was insoluble in soap but that i t would dissolve to a certain extent in the presence of naphthalene, the latter being known t o be soluble in it PICKERING THE DETERGENT ACTION OF SOAP 57 EXPERIMENTAL. Su b s t a m es Us ed. Potassium Stearate.-This contained after drying K = 12.65 ; calc. K=11*99 per cent. It dissolved t o form a 20 per cent. solution a t looo from which on cooling nearly the whole of the stearate separated in a very fine state of division the mixture forming a thick paste. This paste was used in the following experiments. Another and apparently less pure sample contain-ing K=12*96 per cent. was used in a few cases; the results obtained with it differed somewhat in magnitude from those with the first sample.Potassium palmitate behaves with water in the same way as the stearate. The sample used contained K = 12.65 ; calc. K = 13.06 per cent. Potassium oleate was examined only sufficiently to show that the action with it was substantially the same as with the stearate and palmitate. A soft potash soap known as “Chiswick Imperial,” made by the Yalding Manufacturing Go. formerly the Chiswick Co. It is manufactured chiefly from soya-bean oil and contains 8.4 per cent. of potassium oxide as soap and 1.15 per cent. as carbonate. Most of the glycerol has been extracted from it,* and the water lost a t looo amounted t o 47.6 per cent. This soap therefore con-tains about 50 per cent. of dry soap. It is stiff fairly transparent, and undergoes very little hydrolysis with water.A soft soda soap which has been used as a substit’ute for the above since the war began. It’ contains 7.15 per cent. of sodium oxide as soap and 0.53 per cent. as carbonate and hydroxide. Water 42 per cent. It is somewhat. less transparent than the potash soap melts and dissolves less readily being scarceIy fluid a t looo and gives a considerably larger proportion of acid soap when dissolved. One or two other soft soaps have been examined and were found t o behave in the same way as the above; this was also the case with hard soap. The oils used were: A. Paraffin oil freed from olefines sp. gr. a t 1 5 O 0.713 b. p. B. A similar oil sp. gr. 0.784 b. p. 196-200° consisting mainly 90-96O consisting therefore mainly of heptane.of dodecane. * From observations on the subjcct i t appears that glycerol would be without action on paraffin oil in the present experiments 88 PICKERING THE DETERGENT ACTIOK OF SOAP. C . A similar oil sp. gr. 0.815 b$ p. 255-260° consisting mainly of pentadecane. 1). Pratt’s motor spirit sp. gr. 0.697 initial b. p. 7 5 O 58 per cent. of it boiling below 100O a i d 28 per cent. between 100O aiitl 1 2 5 O . E. “ Royal Daylight” lighting oil sp. gr. 0.803 initial b. p. 165O 39 per cent. of it boiling below 250°. 3’. Carless’s solar distillate sp. gr. 0.858 initial b. p. 240° 94 per cent. of it boiling above 250O. C:. Pure benzene sp. gr. 0.85 b. p. 80*5O. E mdwio 11s. As shown in previous communications (T.1907 91 2001; Reports of the Woburn Experimental Fruit Farm 1906 6 196; 1908 8 IS) paraffin oil when churned with a soap solution forms a milky liquid from which the true emulsion gradually rises t o form a creamy layer containing from 65 to 85 per cent. by volume of oil generally about 74 per cent. which is the volume occupiecl by close-packed spheres of uniform size By the further churn-ing of this cream with more oil the percentage can be raised even t o 99 per cent. the emulsion becoming a stiff nearly transparent jelly i n which the oil globules must approximate in form to dodecahedra there being no longer sufficient medium left to allow of their remaining spherical. Viscidity characterises all emulsions, and on emulsification it appears suddenly the resistance to motion of t h e oil particles increasing very rapidly when these become reduced below a certain diameter.The low surface tension between oil and soap solutions must favour emulsification by facilitating the breaking up of the liquids into minute globules but it cannot explain why one of the liquids, and not the other should remain broken up; moreover Hillyer has shown (Zoc. cit. p. 524) that the surface tension is reduced continuously with an increase in the concentration of the soap solution whereas the emulsifying power of such solutions increases with concentration only up to a certain point (about 2 per cent.), and eubsequently decreases (T. Zoc. cit. 2018 ; Woburn Report, 6 197). This behaviour is in accordance with the author’s ex-planation t h a t the emulsification is due to the encasement of the oil particles by minute particles of solid for example of acid soap in the case of soap solutions which view was established by show-ing t h a t the mere presence of solid particles in a fine state of division such as the freshly precipitated basic sulphates of metals, is sufficient to emulsify oils in water itself.It has also become emphasised by the author’s recent work showing t h a t in man PICKERING THE DETERGENT ACTION OJ? SOAP. s9 scores of cases metallic salts of organic acids are precipitated as emulsions the media in such cases being saline solutions which would not exhibit any exceptionally low surf ace tension. The present and recent work necessitates a qualification of one statement originally made namely that the emulsified substaiice must be insoluble in the menstruum.This should be modified t o read t h a t in a permaize, t emulsion the emulsified globules must be in a coiidition such as to preclude them from dissolving the menstruum. The substance composing them may itself be soluble in the menstruum but the globules may be precluded from dis-solving either by the menstruum being already saturated with the substance in question or by the globules being enclosed in a pellicle which prevents their contact with the menstruum. We may even have an emulsion in which the emulsified substance and the nienstruum are identical (see p. 96). Numerous instances have been obtained of substances being precipitated as emulsions which redissolve immediately hence the necessity of introducing the word “ permanent ’’ in the above st’aternent.Behnviour of Sonps with Oils. In the following experiments the quantit,y of soap taken was generally 30 or 60 grams heated to 55O so as to render it less viscid although this heating is not absolutely necessary and was dispensed with when a diluted soap was used. With potassium stearate and palmitate 50 grams of the cold paste containing 13 grams of the salt were employed. The oil was added to these substances and the mixture worked with a spatula. With soap and paraffin oil the incorporation often requires some time the soap slipping about in the oil a t first but when the last of the oil is absorbed the mixture suddenly becomes opaque and almost solid and adheres to or “wets,” the containing vessel.With the soda soap the final mixture is almost transparent instead of opaque. These mixtures are quite permanent provided concentrated soap has been used. When treated with excess of water they dissolve completely forming solutions which are either clear-except for the presence of some acid soap-or if the proportion of oil is larger milky owing to the presence of an emulsion which rises to the surface as a cream in the course of some hours or days. The sudden solidification a t the final absorption of the oil is not indicative of chemical combination and seems to be merely the result of the oil globules attaining a diameter sufficiently small for them t o show the resistance characteristic of emulsions. A similar sudden change t o a stiff opaque mass occurs when water, or even air is worked up with the soap the only difference in such E 90 PfCKERING THE DETERGENT ACTION OF SOAP.cases being that the products are not permanent.; in the case of water the soap gradually dissolves leaving a clear jelly; in that of air the bubbles gradually coalesce leaving a coarse honey-combed mass. The volume of the air particles enclosed in such a mixture is about 50 per cent. of that of the soap. The possi-bility of incorporating water with fats or melted waxes was first recognised by Galen since which time product,s thus obtained have been in use as cosmetics cold cream being one familiar instance. They exhibit some of the properties of emulsions due t o the enclosed globules being comparable in size with those in emulsions, but as the globules are not encased in a pellicle their permanence depends on the semi-solid condition of the menstruum.Mercurial ointment is another instance. Air may similarly be enclosed in soft caramel as is done in the manufacture of sweetmeats exhibit-ing a silky texture. In the incorporation of oil with soaps three stages may be recognised; they are most marked in the case of potassium stearate paste and benzene. The first consists of a thickening of the paste, due t o the incorporation of the oil t o form a coarse sort of emulsion, with a consequent increase in the extent of the oil-water surface; then the mixture becomes limpid due as will be shown to the gradual combination of the oil with the solid stearate to form a soluble compound ; lastly this liquid whether the stirring be continued or not rapidly solidifies to an opaque stiff mass this stiffening being the result of the globules of oil present becoming reduced, by combination with the stearate t o a magnitude sufficient to permit of their forming a true emulsion.The extent to which these stages are marked depends on the proportion of emulsion formed, the viscidity of the reagents and other factors. With potassium palmitate and benzene no final thickening occurs ; with potassium stearate and paraffin oil a slight thickening only is observable; with concentrated soap and any of the oils the only change is a considerable thickening but with less concentrated soap the mix-ture afterwards becomes quite limpid although this change is not followed by a subsequent thickening.With undiluted soap there is a definite limit to the volume of paraffin which may be incorporated with it but in the case of soap previously diluted with one to two volumes of water or in that of stearate paste no definite limit is evident especially with benzene any excess of oil mixing with the solution and on being left rising to the surface mixed with the emulsion PICKERING THZ DETERGENT ACTION O F SOAP. 91 Method of A~zalysis. I n order to examine the nature of the product obtained this was dissolved in a volume of water equal to nineteen times that of the anhydrous soap (9.5 times that of the actual soap) or stearate present. The solution was left in a separating funnel f o r one to three days f o r the emulsion t o rise to the surface and the volume of the latter retaining unavoidably some of the solution deter-mined.Acid was then added to this and the liberated oil-with some fatty acid dissolved in it-measured after which 10 G.C. of the original solution were added and the volume of oil redeter-mined. The measurements give the data for calculating the oil in the emulsion itself and hence that' remaining dissolved in the liquid. The extent to which uniformity is obtainable may be judged by the following results: 30 C.C. of solar distillate with 100 grams of soap." - Dissolved. Ernulsifiod. 21.8 8.2 23-6 6.4 22.6 7.4 Mean 22.7 7.3 30 C.C. of solar distillate with 100 grams of soap diluted. stearate as paste. - v-Dissolved. Emulsified.Dissolved. Emulsified. 1.0 29.0 85 65 0.8 29.2 85 65 2.2 27.8 84 66 1.3 28.7 85 65 150 C . C . of benzene in 100 grams of * Wherever soap is mentioned in the following tables without the quali-fication of " anhydrous " i t refers to the soap in its ordinary condition, that is containing 50 per cent. of water. Thus errors of 1 to 2 C.C. may be expected in the value when relerred as above t o 100 grams of soap. Effect of Manipulation Temperature and Dilutioiz. Differences in the manipulation do not much affect the results; for instance taking a stearate mixture diluted sufficiently (to 5 per cent.) t o admit of its being churned with a syringe the following results were obtained : Benzene to 100 Grams of Dry Stearate. D issolvcd. ,- , Taken.When churned. When not churnotl .................. 100 C.C. 69 70 200 C.C. 86 104 .................. Thus churning increases the prdportion of oil emulsified but No recognisable difference oiily appreciably so in extreme cases. a* 92 PICKERING THE DETERGENT ACTION OB' SOAP. was made in the results whether the oil were added gradually or all at once. A rise of temperature increases the proportion of oil dissolved, although not t.o such an extent that accidental temperature varia-tions would produce an appreciable effect. Solar Distil7ntc and Soap. Temp. Taken. Dissolved. 47" 30 C.C. 21-9 C . C . to 100 grams of soap. 66 30 7 24.9 5 7 7, 90 30 , 254 , , Y , Bestzei~~e and Stearate. (Second sample p. 87.) 17" 150 C . C . 74 C.O. to 100 grams of stoarate.55 150 , 89 y ,7 Y > The validity of the method adopted for analysing the product must depend on the product not being decomposed by water and this was proved to be nearly strictly the case by the followiiig experiments. Lighting oil was incorporated with potash soap in the proportion of 40 C.C. to 100 grams and when dissolved in water equivalent t o x times the volume of soaIi present gave: Xr; 3 6 9 15.5 Oil dissoIved - 34.2 34.4 35.0 36.0 C.C. Again a product containing 69 C.C. of benzene in 100 grains of soap after being dissolved in 950 C.C. of water was further diluted twenty- and one hundred-fold but gave no trace of decompositioii. Similar results were obtained in other cases. That water should not separate any of the oil from the product appears a t first sight (although the explanation will be found below p.94) to be inconsistent with the fact that dilution of the soap before treatment with oil generally results in a reduc-tion of the proportion of oil dissolved. Thus if the soap is previously diluted to the full extent adopted in these experiments -9-5 volumes of water-only about half as much oil or in some cases less passes into solution as when undiluted soap is taken, and the product subsequently diluted the temperature of the reagents being the same in all cases (550). Oil dissolved when the soap was diluted. Oil added. Before adding oil. After adding oil. 33 C.C. lighting oil ......... 7-2 C.C. 18-5 C.C. 67 . , ........... 17.7 , 29.9 ,, 33 , solar distillato.. .... 4.4 Y Y 20.6 ., 67 Y Y 9 ......11.4 , 83.8 ,, The effect of previous dilution of the soap taken is more fully shown in the following series. Taking the determinations wit PICRERING THE DETERGENT ACTT'ON OF SOAP. 93 soap and lighting oil or benzene it will be seen t h a t the amount of oil dissolved decreases with an increase in the proportion of water present but only up t o a certain point after which it remains constant. This point depends on the proportion of oil; with 33 C.C. of oil to 100 grams of anhydrous soap (1) it occurs a t about 900 C.C. of water with 80 C.C. of oil (2) a t about 500 C.C. of water and with 300 C.C. of benzene (7) a t about 100 C.C. of water, or less. The values enclosed in brackets cannot be considered in this connexion for in those cases the benzene was insufficient to saturate the soap? and the product dissolved completely without forming any emulsion.The results with potassium stearate do not offer any instance where constancy was attained b u t with potassium palmitate it occurs with 150 C.C. of benzene (16) when the water reaches 900 C.C. With the palmitate the values are, however not very trustworthy owing to the difficulty of analysing the product the layer of oil and palmitic acid obtained not pre-senting a well-defined meniscus. TABLE I. Volume of Oil Dissolved per 100 Grams of Anhydrous Soaps nt Va ri o zc s Dilu ti o n s. 1 2 3 4 5 G 7 8 0 1 0 11 12 13 14 15 1 (i 1 7 * Oil dissolved (c.c.) by 100 grams of soap diluted with Oil ..-a. 1 taken 200 200 300 400 500 900 1400 1900 C .C . C.C. C . C . C.C. C.C. C.C. C.C. C.C. C.C. Pot,ash soap and lighting oil. 33 20.4 21.8 18.6 - 13.0 3.2 - 3-6 80 63.2 23.2 19.4 - 5.G 2.8 - 5.4 G7 (67) - (G7) - ( 6 7 ) -100 (100) - - - - -Potash soap aid Benzene. - -- -- - 133 122 - 104 - 90 -200 128 -ROO 138 - 134 - 13G -- - - - - -- I Potassium stearate and benzene. 50 - - - (SO)* - - - -75 - - - 69* - 5s 49 -100 -150 - - - 116 - 57 40 -200 -I - - - I 9G -121 - - - - - -Potnssiufii palmitat,c and benzene. - - - - - 47* -60" -76* -50 -75 - - - ria* - GO* 41* -100 -I50 - - - 79" - 46" 47" 48" 200 -- - - - -- - - - I [n these eases uncombined stearat<' or palmitate is present and gradually settles in the liquid 94 PICKERING THE DETERGENT ACTJON OF SOAP.These facts have an important bearing on the use of soap as a detergent. To obtain the most economic results the soap must evidently be used a t the maximum concentration possible; this in practice is done when washing our bodies but not always in other cases. The importance of doing so may be illustrated by smearing the hands all over with paraffin oil when it will be found that the use of 3 grams of soap (which at first slips about in the hands, and then suddenly becomes stiff and adherent) and a subsequent rinsing in a litre of water will suffice to remove the oil; whereas washing them in a litre of water with 3 grams of soap previously dissolved in it is quite ineffectual. The fact that the compounds of oils with soap are not decom-posed by water is also essential t o the detergent action of soap, for otherwise rinsing with water after the application of the soap would regenerate the oil.Looking down the columns in table I it would appear a t first sight that the action between oils and soaps presents features inconsistent with the characteristics of chemical combination o r dissolution f o r the solubility of the oils seems t o be dependent on the proportions present thus although stearate of a given concentration will dissolve 121 C.C. of benzene per 100 grams yet when 75 or 100 C.C. only are added even the whole of these smaller volumes are not dissolved and in some of tlhe cases marked by asterisks a portion of the oil remains uncombined although there is evidently uncombined soap present also.The explanation of this is that a part of the oil added-so long as i t is present in considerable proportions-always becomes emulsified in the manner already indicated and that once emulsified i t is no longer soluble, the particles being protected from contact with the liquid by the pellicle surrounding them. There is however no constant proportion between the oil dis-solved and emulsified; thus with potash soap and benzene the proportion dissolved decreases with an increase in the amount present varying from 100 t o 46 per cent. of the total. The encasing of the oil globules by particles of acid soap must be a process requiring some time and if the actual quantity of oil present is small the dissolution of it will be rapid and there will be less opportunity for the globules to become thus encased.Dilii-tion with water by increasing the qua-ntity of acid soap would increase the proportion of oil emulsified in spite of the fact that the compound of soap and oil is not itself decomposed by water an apparent anomaly alluded t o above (p. 92) PICRERING TRE DETERGENT ACTION OF SOAP. 95 Composition of the Products. Taking the results with stearate and benzene where both reagents are of definite composition; the benzene dissolved by stearate of any given degree of concentration appears to attain a value beyond which a further increase in the proportion of benzene taken would produce little or no increase in the amount dissolved. Taking 1 2 1 C.C. as the maximum in the case of the most concentrated stearate this represents 4.5C,HG t o each C18H3502K and with the two more dilute liquids examined 2.2 and 1.7C,HG respectively; these quantities are in direct pro-portion to the concentration the values obtained by dividing them by the percentages of stearate being 0.23 0.22 and 0.25, respectively.If such a proportion holds good for all concentra-tions the anhydrous stearate should combine with 23C,H, o r 100 grams with 620 C.C. It has not been possible t o realise this prob-ably owing t o anhydrous stearate being in a much less finely divided condition than that in the paste; some digested with benzene a t the ordinary temperature for forty-eight hours com-bined with (that is rendered soluble) only 108 C.C. per 100 grams. The solubility of benzene in soft soap it will be seen is about 70 C.C.per 100 grams or 140 C.C. per 100 grams of anhydrous soap, somewhat more than that of benzene in the most concentrated stearate examined ; its solubility in potassium palmitate is con-siderably less about 80 C.C. The conipound formed in all these cases is quite insoluble ;n the excess of benzene. Sodium stearate i t may be remarked unites with very large proportions of alcohol. A solid fuel known as spiritine coiisists of 95 parts of alcohol and 5 parts of the stearate; but it appears to be a mechanical mixture only the alcohol being imprisoned in a network of crystals of the stearate from which i t can easily be withdrawn by blotting-paper. No such withdrawal is possible in the case of the compounds of oil with soft soap and these more-over are scarcely inflammable.Even when they contain such a readily inflammable oil as benzoline they cannot be ignited unless the proportion of oil is about 67 t o 100 of soap and even then the flame generally dies out as soon as the match is withdrawn. The combination of oils with stearate o r ordinary soap was also examined by leaving the reagents in contact with each other. In the course of a few days a layer of clear limpid liquid began t o form between the viscid stearate or soap and the supernatant oil; this slowly increased in bulk until all the soap disappeared. At the same time an opaque layer gradually formed between the clear layer and the oil; this consisted of an emulsion. Th 96 PICKRRINCY, THE DETERGENT ACTION OF SOAP.emulsion formed in a case where benzene was used was separated and analysed the excess of benzene being removed by filter-paper. It was found to contain 84 per cent. of benzene and as i t evidently contained excess of soap solution which could not be removed the true percentage of benzene in the emulsion must have been higher. It is therefore an emulsion of benzene not an emulsion of soap solution and it presents the curious phenornenon of an emulsion in which the emulsified substance and the menstruum are the same each emulsified sphere being surrounded by a pellicle prob-ably consisting of solid particles and also by some of the aqueous solution which keeps it from coming into contact and coalescing with the menstruum. The spontaneous formation of an emulsion between two liquids in contact with each other and at rest is also somewhat remarkable; the locus of its formation appears to be chiefly the sides of the containing vessel and it is probable that the breaking u p of the liquid into globules is dependent on changes of temperature or unavoidable vibrations.Where ordinary soap is used in such experiments it should be diluted with about double its weight of water since with concentrated soap the clear layer which begins to form between the liquids seems t o be soon absorbed by the soap and renders i t opaque. The results obtained with various oils and potash soap are given below and it will be seen especially when comparing those with the three purified paraffin oils that the proportions passing into solution are not dependent solely on the physical properties of the oil for those with oil boiling at 257O are intermediate between those of the two oils boiling a t 9 8 O and 1 9 8 O .A similar depend-ence on the chemical nature of the oil is evident on a comparison together of the results with petrol lighting oil and solar distillate, or of those with benzene and the paraffin oils. Volume o f Oil Dissolzird b y 100 Grcxms of Soap. Oil Petrol. Lighting. Solar. Parafin b.p. taken. .')so. 19'9". 25yo. Benzene. - 13 - 14 13 23 24 19 21 (33) 37 17 (2167) ;g 33 50 32 22 28 - 22 23 (50) 67 44 25 40 35 30 24 61 64 Where the values are enclosed in brackets the oil was not in sufficient proportion to saturate the soap. The combination oil and soap when the two are worked together, generally occupies about fifteen minutes.The 'course of the reaction may be followed by checking it a t different stages this being clone by the addition of a large volume of water. Potassium - - - 100 62 4 PICRERING THE DETERClENT ACTION OF SOAP. 97 stearate paste and benzene when examined in this way rising 200 C.C. of benzene to every 100 granis of stenrate present gave: OG C.C. clisrolvccl a t the first thickening. SG C.C. , , , snl:sequent thiiuiing. 104 r.c. , , , final thiclceriing. In another case using 150 C.C. of benzene and 100 grams of potash soap there were: i O C . C . disholvccl when tlic inilvturc had thinncd. 84 C.C. , after the f i r i d thickening. T h er rti a I C k a ti g es , The thermal phenomena attending the interact ion between oils and soap are equally emphatic as to the dependence of the results o n the chemical character of the oils taken.The temperature changes occur slowly and continuously throughout the three stages of the reaction (p. go) arid apparently for some little time after the final thickening has occurred. This slowness of the action and the semi-solid condition of the products rendered any accurate thermal determinations impossible. I n the following cases either 50 grams of a 20 per cent. stearate paste or 30 grams of potash soap diluted with 60 grams of water were used. The actual temperature alteration (initial temperature 1 5 O ) is entered anti t h a t per gram of oil dissolved. The determination of the oil dis-solved in the case of the paraffin oils and stearate was however, impossible as the emulsion could not be separated from the un-dissolved st ear ate.Ternpersttiire Evolution pcr g m n dissulvd. 7 alteration. -7 /-St'oarntc with 20 C.C. henzene ... - - 2O.05 - O".OR:i - 2Fi Crtl. Soap , 20 C . C . benzene ... - - 1 .58 - 0 -102 -11.2 cal. I , 10 C.C. parallin b.p. 93" -0 a 2 0 -0 . 0 % 1 -4-6 ,, 3 7 ). 10 C . C . , ,) lss' +o -26 -\-0 .OdO 4-8.8 ,, 9 .) 10 C . C . ) ) ,) 8570 +o -1s ~ 0 -340 +87.4 ,) It will be seen that the magnitude and sign of the thermal disturbance depends on the nature of the oil used; doubtless the combination of it with the soap is exothermic in all cases but the heat evolved is generally more than counterbalanced by t h a t absorbed in t'he attendant fusion of the solid stearate or of the semi-solid soap.- - 3 , 10 C.C. p"l'"fliI1 13.p. 9 3 O -0 -35 7 , 10 C . C . ) ,) 257O +0 *30 - -Naphthnlei~e and Soap. Cousins in the little book already mentioned claims that as the results of '' exhaustive experiments " he had established tha 98 PICKERINQ THE DETERGENT ACTION OF SOAP. the presence of naphthalene greatly assists in producing (‘a paraffin emulsion of a kind and perfection superior to that obtain-able with paraffin and soap alone,” and he secured a patent (1895, No. 13201) for such a substance f o r use as an insecticide under the name of paranaph the directions for the preparation of which were melt 100 grams of soft soap with 38 parts of water; then dissolve 10 parts of naphthalene in it after which 16.7 volumes of paraffin oil are incorporated in it The results of these exhaustive experiments have however never been published and no evidence seems to exist that the insecticidal properties of such a substance are greater than those of ordinary paraffin emulsion (see J .8.-E. Agric. CoZZ. 1896 5 51 where some trials on hop aphis are given, but without comparison with those obtained with other insecti-cides). It is not clear in what condition Cousins considers the paraffin to be present in this substance for he states that “it dissolves readily in cold water so as to give a milky emulsion-from which no visible separation of oil takes place even after standing for several weeks in open air.” But if the paraffin is dis-solved it is not present as an emulsion and if i t is emulsified i t is not dissolved and in the latter case would certainly (in part a t any rate) rise to the surface for its specific gravity would be about 0.9.The facts of the case appears to negative all Cousins’s contentions; paraffin oil as has been seen dissolves in soap without the addition of naphthalene ; naphthalene on the whole diminishes its solubility; the greater part of the naphthalene separates from the liquid on dilution and if the paraffin is present in such pro-portions as not t o be entirely dissolved the excess rises t o the surface as an emulsion. The behaviour of naphthalene with soap exhibits none of the peculiarities shown by paraffin; i t dissolves t o a sinall extent in heated soap rendering it more liquid but on cooling some of the naphthalene separat’es in the crystalline form.The solubility seems to be increased by the addition of a little water but, diminishes on further dillition. Thus with potash soap : Soap ... 4-100 + 100 + 100 f 100 -b 100 -1-100 t-100 + Water. 0 100 200 300 G 0 0 1000 2000 but the values with the more concentrated soap solutions (enclosed in brackets) are very uncertain as the liquids cannot be filtered PICKERING THE DETERGENT ACTION OF SOAP. 99 and cannot be diluted without altering their composition ; whether the naphthalene has dissolved or not has t o be determined by the clearness of the solution and this is interfered with by frothing. I n another instance 10 grams of naphthalene were digested a t looo with 100 grams of soda soap previously diluted with 38 C.C.of water and the product after cooling dissolved in x C.C. of water; the results were : x= 300 naphthalene remaining dissolved = 1-8 grams. X = 600 = 1.5 , 5 ? 9 9 ,) z = 1000 Y Y ? 9 L= 1.3 ,, z = 2000 9 7 9 9 9 9 = 0.9 ), A considerable tendency for the naphthalene to remain in a state of supersaturation for many hours was observed in these experiments. When to a solution of naphthalene in soap paraffin oil is added, and the product dissolved in water then according t o the propor-tions of the reagents taken there occurs either complete dissolu-tion or partial dissolution with the separation of some emulsion and crystallised naphthalene which latter either sinks to the bottom or becomes entangled in the emulsion at the top.Much of the naphthalene must also be dissolved in the oil globules since its solubility in lighting oils is 1 2 grams in 100 C.C. a t 1 5 O . I n the following experiments 10 grams of naphthalene (volume 8.7 c.c.) were dissolved in 100 grams of soap then worked with oil and the product dissolved in 950 C.C. of water. The emulsion was determined in the usual way and any deposit of naphthalene in the liquid separated and dried. The data obtained gave the volume of oil + naphthalene which remained in solution (entered in column 11); the volumes taken are entered in column I and the volumes of each which would remain in solution if either the oil or the naphthalene had each been present alone as determined by separate experiments are given in column 111 whilst the differ-ence between the sums of these latter volumes and of that dis-solved when the two substances are present together are given in column IV.In Nos. 8-10 38 C.C. of water were previously added to 100 grams of soap so that in No. 8 we have the same proportions of all the substances as in Cousins’s paranaph the soap however, being soda instead of potash soap and in soda soap the whole of the oil becomes dissolved without the formation of any emulsion. It will be seen from Nos. 6 7 and 10 where the volume of oil taken is large that the presence of naphthalene results in a con-siderable reduction in the volume of oil dissolved the volume of oil+naphthalene dissolved being even less than that of the oi 100 PTCKERING THE DETERGENT ACTION OF SOAP.TABLE 11. Waphthalene (N) and Oils Dissolved in 100 G r a m of Soap. Volumes dissolved. Volumes taken. Taken together. Taken separately. Difference. I. 11. 111. ZV. N. S.7 1 2 9 9 3 4 I i L. 3i:3 N. 8.7 5 6 L. o6r7 N. 8.7 7 9 , Potassium soap and lighting oil. 255.4 (L). ''*' 1 1G.3 -0-1 7 N. 2.1 J N. 2.1 J i i 16.2 13.7 7 1,. 18.5 \ 20.6 - 0.3 29.7 15.2 42.0 21.6 7 9 32.0 - 7.2 L- 28*9 1 19.0 I 20*3 24.8 N. 2.1 J 75*4 25.5 'I , 24-2 J Soda soap (diluted) and lighting oil. -f- 7.4 8 L. 16'7 ) 25.4 25.4 18.0 16-7 N. 8.7 2.3 L. 33.3 9 42.0 22.8 22.7 '1 24.0 - 1.2 N. 8.7 1 1.3 J Soda soap (dilntod) and Bcnzene. (€3). 47.5 7.5.4 35.1 - 49.0 -13.9 1-3 j B.6G.7 N. 8.7 10 dissolved when oil alone is taken. Where however the propor-tion of oil taken is smaller (Nos. 1-4 and 9) there is a similar reduction although quite insignificant in amount. I n No. 8, however we have an exception the presence of the two substances together resulting in much more of them being dissolved than when they are taken separately; but this increase is due not to more paraffin but to more naphthalene having been dissolved for the whole 8.7 C.C. of this substance instead of only 1.3 c.c. have remained in solution. Doubtless this is an accidental case the naphthalene having remained dissolved in a state of supersatura-tion ; nrid in one or two other cases besides those already mentioned (p. 99) i t was noticed that a similar supersaturation was main-tained until the liquid was drawn off from the emulsion.Such an instance however lends no support t o the view t,hat naphtha-lene increases the solubility of paraffin MERCURY MERCAPTIDE NITRITES AND THElR REACTION ETC. 101 Sum mar y . The detergent action of soap is due in part to its power of emulsifying oil the oil globules of which become enclosed in a pellicle which prevents them rendering contiguous substances oily ; in part t o the lowness of surface tension between oil and soap solution; and perhaps in part to the union of dirt with the acid soap produced by hydrolysis. A more important factor is that oils even paraffin oils dissolve in soap to form soluble compounds, which contain in some cases nearly equal weights of oil and soap. Except when the oil added is small in amount a certain propor-tion of it becomes emulsified and incapable of combining with the soap owing to the protecting Fellicle hence considerable excess of oil must be taken for the soap to combine with the maximum amount of oil possible. The compound formed is not decomposed by excess of water but dilution of the soap previous to its treat-ment with oil results in much less oil combining with it because a larger proportion of the latter becomes emulsified. The combination of soap with oil is accompanied by a series of physical changes explicable by the nature or" the products formed-a soluble limpid compound on the one hand and ail emulsion which is almost solid on the other. The proportions of oil and soap which will unite with each other depen9 on the chemical and not merely physical nature of the reagents and an appreciable heat-disturbance either negative or positive accorri-panies the reaction. Naphthalene does not behave towards soap as paraffin does but dissolves in i t t o a limited extent some of the crystalline substance separating 0x1 cooling or dilution. The presence of naphthalene decreases the amount of paraffin dissolved by soap. HARPENDEN. [Received Junuaq 19th 1917.

ISSN:0368-1645    

DOI:10.1039/CT9171100086

出版商:RSC    

年代:1917

数据来源: RSC

摘要:

MERCURY MERCAPTIDE NITRITES AND THEIR REACTION ETC. 101 XI.-Mercury Memaptide Nitrites and tl&r Reaction with the Alkyl Iodides. Part 111. Chain Com-pounds of Sulphw. By PRAFULLA CHANDRA RiY. THE present communication deals mainly with a class of thio-compounds which may be conveniently termed potential mer-captans. Thiocarbamide as also the substituted thiocarbamides 102 RAY MERCURY MERCAPTIDZ NITRITES AND THEIR thioacetamide and thiobenzamide may be among others placed under this group. It has already been shown that under the influence of suitable reagents for example monochloroacetic acid, iodine etc. some of them assume the tautomeric form of imino-mercaptans and thus become reactive (T. 1914 105 2159; and T. 1916 109 698). It occurred to the author that a class of corresponding nitromercaptides might be obtained from these by reaction with mercuric nitrite and from the latter again a new series of disulphonium compounds.This anticipation has not been realised in the expected direction. The main interest in the investigation would however seem to centre round the fact that a series of chain compounds of sulphur has been obtained some containing as many as six sulphur atoms. The isolation of the long expected dimercuric di-iododisulphide I*Hg*S*S*Hg*I has also been effected. Thiocarbamide for instance under the influence of mercuric nitrite would be expected to yield the compound thus : NH,= C( S-HgNO,) :NH, NH2*C(SH):NH + Hg(N02) = NH2*C(S*HgN02):NH -F HNO,. This reaction actually proceeds as indicated above but the result-ing compound has been found to be incapable of existence as such; in the nascent stage it assumes the stable form by the conversion of the bivalent into the quadrivalent sulphur atom by fixing a molecule of mercuric nitrite thus : H-gN 0, 1 HgNO, I (compare T.1916 109 133). Thiocarbamide however yields the above compound only under special conditions which are described in detail later. The main product of the reaction is also a nitrite but a purely inorganic one having the formula 3(SHgNO,),HgO. Before we discuss its constitution further it is necessary to add that the mono- and di-alkylated thiocarbamides thioacetamide thiobenzamide as also the thiocarbimides by reaction with mercuric nitrite yield the same substance REACTlON WITH TILE ALKYL IODIDES.PART 111. 103 Mechanism of t h e Reaction. Thioacetamide and thiobenzamide will be first considered. Under the influence of mercuric nitrite they assume the tautomeric form thus: R*C(:NH)*SH (where R is an alkyl or aryl group), and the initial reaction is as follows: R*C(:NH)*SH + NO,* Hg*NO,= R*C(:NH),S.HgNO + HNO,. Scission however takes place as shown by the dotted line. The radicle R*C( :NH)- acting on three molecules of water generates acet- or benz-aldehyde as also the corresponding acids with the elimination of two molecules of ammonia, 2Ll*C(:NH)* +2H,U+H~OH=R*C0H+R.CO2H+3NH,. The radicle *SHgNO, on the other hand might be expected to condense to NO,HgS*SHgNB ; the compound actually formed is, however an oxidation product of the formula NO,HgS*O*SHgNO ; the liberation of nitrous acid as shown above evidently assists this process.This compound is however formed only in rare instances; in nine cases out of ten the radicle assumes the more stable form 3($HgNO2),Hg0. Thiocarbamide and its alkylated derivatives equally yield this substance. It is only in the case of thiocarbamide and under special conditions that the compound shown above is formed; here also scission takes place as shown by the dotted line thus: N H,* C( N 11 ) S- Hg NO,. The radicle *SHgNO becomes detached and exists in the per-manent form 3(SHgNO,),HgO. I n the filtrate ammonia is found in quantity; whilst in the case of the interaction of diethylthio-carbamide and mercuric nitrite instead of ammonia ethylamine is obtained.It is worthy of note that in the case of mono- and di-alkylthio-carbamides no tendency towards the formation of the intermediate sulphonium oxynitrite has been observed. This is what might have been expected. The molecule being already loaded with one Gr two alkyl groups a t once decomposes and does not lend itself to the formation of the cyclo-compound. The carbimides also yield the same product namely, 3( SHgNO,),HgO although they cannot behave as imino-mercaptans. Here also it is the tendency of the bivalent sulphu 104 RAY MERCURY MERCAPTIIIE NITRITES AN11 THEIR atom to beco,me quadrivalent that may be regarded as the under-lying principle of the reaction thus : The rupture takes place along the line of least resistance and the radicle >S<HgN''2 decomposes into the stable radicle *SHgNO with the evolution of nitrous fumes whilst the organic portion of the complex RN:C < with a molecule of water yields a primary amine and carbon monoxide.The formula of the subdance 3(SHgN02),Hg0 is only the empirical one based on analysis; it represents however an un-saturated compound. I n order to obtain an insight into its real constitution the formula should be doubled thus : or w? t3 (SHgNO,) ,HgOl2 HgNQ2 HgNO HgNO S lIgNO, I I I I -s ---I I I Hg-0S.W &&,; :NO No.'O-Wg SS-HgNO = NO,Hg .,3. S-- s-HgNO YgNO Yg-NO IIgNO, I 1 I I I N 0,Hg S * S -S--S-S*S*H gNO + 2 N,O,. Hg O-- Hg-- G I n other words as soon as there is an opportunity for the formation of the stable radicle .SHgNO, every three of these take up an additional molecule of mercuric nitrite (that is the radicles HgNO, and NO,) and the two complexes coalesce into a single molecule with the evolution of two molecules of nitrogen trioxide.On a previous occasion (T. 1916 109 133) in explaining the formation of the compound Et$32Hg(N0,),,Hg0 by the interaction of ethyl disulphide and mercuric nitrite with the evolution of nitrous fumes it was assumed as a working hypothesis that the two ato'ms of bivalent sulphur became quadrivalent. I n the present) investigation this hypothesis has been elaborated and found t o hold good throughout not only in explaining the formation of the compound under discussion but also that of the compound NH,*C(:NH)*S*HgNO, and also the reaction between thiocarb-imides and mercuric nitrite.The hypothesis being in conformity with d l the observed facts now stands on a solid foundation. By treating the compound Hg,S30,N3 which is highly reactive with the alkyl iodides Borne interesting chain com-pounds of sulphur have been obtained notably one of three sulphur atoms having the formula HgI*SEtI*S*SEt in which on REACTION WITH THE ALKYL IODIDES. PART 111. 105 sulphur atom is quadrivalelit and the remaining ones bivalent and dimercuric di-iododisulphide. It is the affinity of the sulphur atom for the radicles *HgI and -HgNO respectively that may be regarded as the underlying prin-ciple in the formation of derivatives of this type. From analogy, also one might have expected a compound of the formula NO,Hg*S*S*HgNO, and not NO,Hg-S*O-S*HgNO,~ b u t the mode of its formation as also of dimercuric di-iododisulphide explains the *difference in their constitution.The former is produced by ' wet ' reaction in the presence of nascent nitrous acid which acts as a powerful oxidising agent whereas the latter is the product of a reaction which precludes the possibility of oxygen taking any part whatever. It will be noticed that whenever there are more than two atoms of sulphur in a molecule some (but Rot all) can become quadri-valent. Thus the sulphonium derivative of ethylene mercaptan, empirically formulated as (C,H,S,),,HgI,,EtI should be repre-sented as ,S- s, O,H,( HgI Et\C,H,, \S-d,/ 5 I / t- t i n wliicli formula only two of the four sulphiir atoms are quadri-valelit) (T.1916 109 605). The componnd has only one quadrivalent sulphur atom whereas in the compouiicl I3( SHgNO,),HgO], containing six sulphur atoms the two extreme members in the long chain are bivalent the intermediate ones being quadrivalent. I n connexion with this it is of interest to note that Auld in his recent investigation on alkali polysulphides (T. 1915, 107 480) suggests t h a t calcium polysulphide should be forinu-lated as Ca<ll>S:S:S t h a t is the sulphur atoms a t one end of the chain are quadrivalent whilst the atom a t the other end is b i v a1 en t , Methyl iodide when heated on the water-bath in contact with the above complex inorganic oxynitrite yields as the main pro-duct besides nitromethane the compound Me2S,,Hg12,MeI which has been previously described (T.1916 109 606) as having been obtained by treating mercury methylmercaptide nitrite with s 106 RAY MERCURY MERCAPTIDE NITRITES AND THEIR methyl iodide. The present reaction however is of interest, inasmuch as a purely inorganic salt and not a nitromercaptide, yields a compound of the disulphonium series. When the higher alkyl iodides are substituted the reaction assumes various degrees of complexity. It may be added here that the compound Et,S,Hg(NO,),,HgO, when heated with ethyl iodide is converted into the corresponding disulphonium compound Et,S2HgI,,EtI. EXPERIMENTAL. Interaction of Mercuric Xitrite and Thiocarbamide. A very dilute aqueous solution of thiocarbamide is added in a thin stream from a 5 C.C.pipette with constant shaking to a fairly concentrated solution (about 100 c.c.) of mercuric nitrite (in the shape of sodium mercurinitrite; T. 1907 91 2031). A curdy, whitme precipitate is formed which should be collected a t once; the operation should in fact be performed within five minutes. The filtrate is set aside when i t begins slowly to deposit a yellow, heavy granular powder; to it is now added from time to time at intervals of twenty minutes to half an hour 5 C.C. of the tliiocarb-amide solution as before. Successive crops of the yellow salt are thus continuously obtained. The reaction should be allowed t o proceed for several hours. During the course of the reaction bubbles of gas are given off and the odour of nitrous fumes is distinctly perceptible.The curdy white precipitate as obtained above when dried in a vacuum over sulphuric acid assumes a very faint yellow tint. It has the constitution HgNO, NH,*C(:NH)-S-Hg \/ I 0 and dissolves in hydrochloric acid evolving nitrous fumes : Found C = 2-00. 0.1222 gave 7.8 C.C. a t 3 2 O and 760 mm. 0.1004 ? 0.0872 HgS and 0.0414 BaSO,. Hg-74.87; CH303N,SHg requires C=2*23; N=7.82; S=5*96; Hg=74*49 per cent. The cornpoutid [3(SHgNO,),HgO] is as explained above the stable modification of that obtained by the interaction of mercuric nitrite and thiocarbamide. The substituted thiocarbamides thio-N=7.00.* S = 5.66. * Another preparation gave N= 7.17 REACTION WITH THE ALKYL IODIDES. PART III. 107 acetamide thiobenzamide and the thiocarbimides yield only this variety to the exclusion of the former.As it was difficult t o believe that the product obtained in each case was an inorganic salt of identical composition it was subjected repeatedly t o com-bustion analysis but the amount of carbon was negligible as it varied from 0.2 to 0.5 per cent. This is no doubt due t o traces of the organic reacting agents being co-precipitated. The compound is heavy granular and yellow and can be dried in a steam-oven. It is insoluble in water o r acetone but dissolves in hydrochloric acid especially on warming with effervescence and copious evolution of nitrous fumes. When boiled with water it decomposes and is converted into black mercuric sulphide : 0-1206 gave 0.1065 HgS and 0.0742 BaSO,. Hg=76*13; 0-1328 gave 0.0838 BaSO,.S=8-66. 0.1172 , 3.8 C.C. N a t 3 1 O and 760 mm. N=3*60. [0*2028 , 0.0012 CO and 0.0036 H,O. C=0*16; H=0*20.] Hg,S30,N3 requires Hg = 76.19 ; S = 9-14 ; N =4.00 per cent. If this compound instead of being removed is left in contact with the mother liquor for a week or sometimes even for a forb night it slowly undergoes a remarkable change in composition a dull red and on some occasions a scarlet modification of mercuric sulphide being produced. The formation of the dull red as also of the crystalline form of the sulphide by the wet process has not so far as we are aware been previously noticed. An analysis of the red sulphide necessarily impure gave Hg = 83-43 S = 14.29 whilst theory requires Hg = 86.20 S = 13.80 per cent.When diethylthiocarbamide is used in the reaction a compound of the formula NO,Hg-S*O*S*HgNO is occasionally also formed : 0.1010 gave 0.0810 HgS and 0.0760 BaSO,. Hg=6*14; 0.1694 gave 5.2 C.C. N2 a t 2 9 O and 760 mm. Hg2S20,N2 requires Hg=69.94; S=11*19; N-4-90 per cent. S=8.45. S = 10.34. N=3*44. Interaction of Mercuric Nitrite and Allylthiocarb imide. I n this preparation particular care should be taken not to add an excess of the thiocarbimide. The following method is recom-mended. A very dilute solution of allylthiocarbimide in alcohol is added in a thin stream with constant shaking to a fairly concen-trated solution of the nitrite. If the former happens t o be present even in slight excess the precipitate at once turns black and i 108 MERCIJRY MERCAPTTDE NITRITES ANT THETR REACTION ETC.ultimately converted into mercuric sulphide. nitrous fumes are evolved. During the reaction The presence of allylamine in the filtrate was proved. Interactioi, of tire Compound I3(SHgNO,),HgO] rind the A 7kyl lOdideS. (a) M c f i ~ y l Zod&-As pointed out above methyl iodide yields the disulphoniurri coitipound Me,S,,HgI,,n'IeI. The method of procedure is exactly the saine as in the interaction of mercury mercaptide nitrites and the alkyl iodides. The product purified by precipitation from its acetone solution with ether melted a t 162O : 0.1552 gave 0.0296 CO and 0*0200 H,O. 0.0864 required 23.1 C.C. AgNO solution in acetone=3'78 C.C. 0.1872 gave 0.0550 Hg. Hg = 29.38. C,H,I,S,Hg requires C = 5-22 ; H = 1.30 ; I =55% ; Hg= 28-95 (b) Ethyl lodide.-In this case the reaction is by no means so simple as above; the mother liquor contains nitroetliane and un-changed ethyl iodide and when it is evaporated a deposit' of red mercuric iodide is left.The yellow residue in the flask is repeatedly exhausted with acetone which dissolves the organic constituents. The insoluble portion consists mainly of impure diiriercuric di-iodo-disulphide I*Hg*S*S*Hg*I. The acetone filtrate on evaporation gives a mass of yellow crystals and by careful fractionation a product melting a t 86--88O can lie separated. I t approximates t o the formula Et,S,HgT or C=5*20; H=1*43. N / lO-AgNO,=O.O48O I. I = 55-60. per cent. IIgI E&S-S*E~ . 1 1 Small quantities of the compound Et2S2,HgI,,EtI (in.p. 1lao) and another substance with a higher melting point are also' among the products. It is not however easy to obtaiii thein in a pure state. Analysis of the Substance Melting a t 86-88O. 0.1372 gave 0.0378 CO and 0-0351 H,O. 0.2412 , 0.0760 Hg 0.1947 AgI and 0.2374 BaSO,. 02234 gave 0.0708 Hg. Hg=31-69. C=7*51; H=2-84. Hg=31.51; I=43*62; S=13*52. C,H,,T,S,Hg requires C = 7-89 ; H = 1-64 ; Ng = 32.89 ; I = 41:77 ; S = 15.79 per cent AZOXYC.4TECHOL ETI-IERS AND RELATED SUBSTANCES. 10'3 Dimercuric di-iododisulphide as prepared in the above manner, is always contaminated with some of the unchanged compound, [S(SHgNO,),HgO],. It was therefore dried powdered and boiled with ethyl iodide this process being repeated and after each treat-ment with ethyl iodide the product was repeatedly exhausted with acetone so as to remove the soluble constituents referred to above: 0.2616 gave 0-1480 Hg. Hg=56*59. 0.2374 , 0.1346 Hg and0.1565 BaS04. Hg=56*170; S=9.05. Hg,I,S requires Hg=55*71; S=8*91 per cent. Dimercuric di-iododisulphide is a pale yellow granular powder. It slowly darkens in diffused daylight; on exposure to direct sun-light this process is hastened but when kept in the dark the original yellow colour is restored. Similar instances of reversible phototropic properties are only met with in the class of organic colouring matters known as the fulgides. I avail myself of this opportunity t o express my siiicere thanks to Mr. M. L. Dey M.Sc. for his ungrudging help in the tedious estimation of sulphur in these conipouncls and for some suggestions as t o their constitution. CHEMICAL LABORATORY, PRESIDENCY COLLEGE CALCUTTA. LRccciucd JLirie Z ' i t h 19lti.

ISSN:0368-1645    

DOI:10.1039/CT9171100101

出版商:RSC    

年代:1917

数据来源: RSC

摘要:

AZOXYC.4TECHOL ETI-IERS AND RELATED SUBSTANCES. 10‘3 X K-Axoxycatechol Ethers and Related Substances. By GERTRUDE MAUD ROBINSON. IT has already been shown that 6-nitro-3 4-methylenedioxy-mandelic acid (I) is changed in boiling nitrobenzene solution into 4 5 4’ 5/-dimethylenetetraoxyazobenzene-2 2’-dicarboxylic acid (11) (Robinson and Robinson T. 1914 105 1466; 1915 107, 1759) and it is now found that the same azo-acid is the main product of the decomposition of the substance by means of a hot’ aqueous solution of sodium or potassium hydroxide. O/\CH(OH).CO,H CH,<ol O’\CO INL--Nl 11 CO,H/)g>CH,. \/ -- \/ CH2< L) (/) N 0, (1.1 (11.1 Under these conditions however about a quarter of the mandelic acid derivative is transformed into a neutral bright yellow crystal-line substance C,,HIoOiN2 which separates from the alkaline solu-tion.The investigation of this compound has demonstrated tha 110 ROBINSON AZOXYCATECHOL ETHERS it is azoxypiperonal (111) and it may be obtained although iii small yield by the action of sodium methoxide on iiitropiperonal in methyl-alcoholic solution. It yields a diphenylhydrazone crystal-lising in red needles and is changed by nitric acid t o a nitro-dime t hylene t etraoxyazox yb enzenecarboxylic acid (IV) which undergoes a complex change in alkaline solution (compare p. 119). Bamberger (Ber. 1911 44 1966) has prepared 2 2’-azoxylueiiz-aldehyde (V) by the hydrolysis of its methyl and ethyl acetals and finds that it undergoes a curious reaction in boiling acetic acid or under photochemical influence resulting in the production of the lactone of 3-hydroxy-o-indazylbeiizoic acid (VI) a substance which had already been obtained by Carre (Compt.rend. 1906 143, 54). This lactone yields azobenzenedicarboxylic acid on oxidation by chromic acid. The close connexion between the indazole group and the ortho-substituted azo- and azoxy-benzenes had already been demonstrated by Freundler in a series of papers (for ex-ample Compt. rend. 1903 136 370). Azoxypiperonal exhibits a behaviour similar to that of azoxybenzaldehyde and is changed in hot acetic acid o r nitrobenzene to the lactone (VII) which resembles the indazole derivative from the simpler substance and yields the azodicarboxylic acid (11) on oxidation with a solution of chromic acid.(VII. AND RELATED SUBSTANCES. 111 The Constitution of the Azosy-compounds.% The attention of the author was directed to this subject by the consideration of the reaction between azoxypiperonal and nitric acid which results as stated above in the production of an un-symmet,rical substance. One of the aldehydo-groups is oxidised to carboxyl the other is displaced by nitroxyl whilst the substance remains a derivative of azoxybenzene. This seemed an anomalous result if the azoxy-compounds have the usually accepted structure A whilst i t would be readily explicable if the arrangement B (compare Briihl Zeitsch. physikal. Chem. 1898 25 577) is con-tained in the molecules of these compounds. 0 0 \-N=N- ‘ I / Now the nitration of veratrole proceeds in sharply defined stages according to the conditions.I n acetic acid solution no trace of dinitro-compound is formed and the yield of 4-nitroveratrole is quantitative. The dinitroveratrole is however produced by the action of nitric acid (D 1.42) on the mononitro-derivative and in this case also the yield approximates closely to that demanded by theory. The azo-group does not inhibit the nitration of the vera-trole nucleus in acetic acid solution and azoveratrole yields dinitroazoveratrole under these conditions. For these reasons it was considered that the behaviour of azoxyveratrole on nitration would afford a criterion as t o the value of the structures A and B as representations for the azoxy-compounds. If azoxyveratrole has the constitution (VIII) of the B-type then one nucleus is approximately in the condition of the nucleus in nitroveratrole, and the other ring is in a condition which cannot differ greatly from that of the nuclei of azoveratrole.I n consequence only a single nitro-group should be introduced in acetic acid solution, whilst the dinitroazoxyveratrole should be obtained by treatment of the mononitro-derivative with nitric acid (D 1-42). On the other hand if the structure (IX) of the A-type represents azoxy-* The author *regrets that a t the time of communication of this paper, the important work of Angeli and Valori on the constitution of the azoxy-compounds had been overlooked and is grateful to the Editor for affording an opportunity to repair this omission. The Italian chemists have brought forward evidence suEcient to establish the unsymmetrical const*itution of azoxybenzene and the priority in this matter belongs to them.The author is permitted to state that a brief account of this interesting work will form a part of the forthcoming “ Annual Reports on the Progress of Chemistry for 1916. 112 ROBINSON AZOXY CATECHOL ETHERS veratrole there appears to be no reason why both nuclei should not be nitrated under conditions which are sufficient to nitrate the substance at all. Azoxyveratrole was easily obtained in good yield by the usual method applied t o nitroveratrole and on treatment with nitric acid in acetic acid solution gave no trace of a dinitro-derivative, but an excellent yield of mononitroazoxyveratrole (X) which by dissolving in nitric acid (D 1-43) was changed to dinitroazoxy-veratrole (XI).The result is strong evidence in favour of the structure (VIII) for azoxyveratrole. Several substances contain-ing two veratrole nuclei symmetrically placed in a single rriole-cule are known and in all cases the two nuclei are simultaneously attacked on nitration. Examples are diveratrylmethane (XII) (G. M. Robinson T. 1915 107 '275) azoveratrole (XIII) (Robinson and Robinson T. 1915 107 1756) and eudesrriin (XIV) (R. Robinson and H. G. Smith J . PTOC. Roy. SOC. N e w South Wales 1914 48 458). Each of these substances yields a dinitro-derivative under the coiiditions of the nitration of azoxy-veratrole to the mononitro-derivative. Bromination in acetic acid solution converts azoxyveratrole into a monobromo-derivative a result which harmonises with the fact that nitroveratrole cannot be attacked under such conditions.0 0 e MeO/\-C,H,O,-('OMe MeCl 1 ,)OMc (XIV.) \/ (XI. ) Since it will probably be conceded that as far as possible the azoxy-compounds should all be represented in a similar manner it remains t o state the opinion that even on general grounds th AND RELATED SUBSTANCES. 113 unsymmetrical structure is a better representation of the proper-ties of the substances than the usual symmetrical one. On the physical side in addition to Briihl's argument from the refractive power there is the pale yellow colour which harmonises better with the idea that azoxybenzene is the phenylimine of nitro-benzene than with the suggestion that this substance is related t o hydrazobenzene in the same way that ethylene oxide is related to ethane.The low melting points and relatively ready solubilities of the members of this group are in a general manner probably due to' their unsymmetrical structure. On the chemical side the author is not aware that any valid argument has been advanced against the structural formulx advocated. The relations with azobenzene nitrosobenzene and phenylhydroxylamine are perhaps a little better represented by the unsymmetrical than by the symmetrical formula. A comparison of the reactivity of the azoxy-compounds and the nitrosoamines has been made by Lachman (Amer. Chem. J. 1899 21 433) who concludes that since the nitrosoamines are much more active than the azoxy-compounds, the latter cannot have a structure of the type B represented above.This comparison however fails since the nitrosoamines contain tervalent nitrogen and the azoxycompounds a quinquevalent nitrogen atom and the diminution of reactivity which accom-panies the conversion of nitrosobenzene into nitrobenzene indicates that it is not possible to compare the nitrosoamines with Bruhl's formula for the azoxy-compounds. It may further be pointed out that on the Hantzsch-Werner hypothesis it is possible t o predict the existence of stereoisomeric modifications of the azoxy-com-pounds either on the basis of the usual structure or that suggested by Bruhl. It is probable that such modifications have been isolated by Reiscyert (Ber. 1909 42 1364). E x P ER I M E N T A L. 4 5 41 5f-D.inzethylenetetraoll;.ya.zoZ,enze~ie, An attempt was made to prepare dimethylenetetraoxyazoxy-benzene by the reduction of nitromethylenedioxybenzene with sodium methoxide in methyl-alcoholic solution and in view of the smooth production of azoxyveratrole which is described below i t is somewhat remarkable that the only product appeared to be a nitrophenol the nature of which is being investigated.However, i t was found possible to obtain the azo-derivative of the piperonyl series in the following manner. VOL. OIX. 114 ROBINSON AZOXYCATECHOL ETHERS Nitromethylenedioxybenzene (1 gram) dissolved in ethyl alcohol (50 c.c.) was mixed with potassium hydroxide (2 grams) and water (8 c.c.) and reduced a t the boiling point of the liquid during five minutes by means of zinc dust (4 grams).The filtered solu-tion deposited yellow platelets on cooling and these were collected and purified by extraction with a very large volume (about 500 c.c.) of very dilute hydrochloric acid. The substance was then recrystal-lised from ethyl acetate and was obtained in long narrow golden plates melting a t 236-237O : 0.0839 gave 7.9 C.C. N2 a t 22O and 742 mm. I n most solvents this compound is sparingly soluble moderately so in hot acetone or benzene and readily so in nitrobenzene. I t s solution in sulphuric acid is purple and a magenta coloration is also developed in acetic acid solution by the addition of a drop of sulphuric hydrochloric or nitric acid. The deep blue solution in nitric acid (D 1.4) quickly becomes purple and the intensity of the colour rapidly diminishes as the substance becomes nitrated.The derivative formed separates from mlution in yellowish-brown crystals and may be recrystallised from nitrobenzene. It is so obtained in bright red needles melting a t 305O with some decom-position and a t the same temperature when mixed with a speci-men of 2 2'-dinitro-4 5 4' 5!-dimethy~enetetraoxyazobenzene obtained by the method described in a former communication (Robinson and Robinson T. 1915 107 1761). N=10*7. C,,H,,O,N requires N= 10.4 per cent. A zoxyverutrole (Formula VIII). A solution of sodium methoxide was prepared from sodium (10 grams) and methyl alcohol (100 grams) and after the addi-tion of 4-nitroveratrole (15 grams) the mixture was boiled under reflux during thirty minutes.Towards the end of this period the product of the reaction separated in glistening needles and, when the operation was finished the mixture was cooled an equal volume of water added and the crystals collected and washed with alcohol. The material so obtained was nearly pure and when dried weighed 11 grams. The substance is sparingly soluble in alcohol moderately so in acetic acid chloroform or ethyl acetate, and dissolves freely in benzene. It is best crystallised from acetone, and is sol obtained in yellow prismatic needles melting a t 155-156': 0.1467 gave 11.4 C.C. N a t 18* and 749 mm. The eubstance dissolved in sulphuric acid to a bright red solu-N=9*0. C,6H1,0,N requires N = 8.8 per cent AND RELATED SUBSTANCES. 115 tion but was decomposed since it could not be recovered after the addition of water.On strongly heating an intimate mixture of azoxyveratrole with clean iron filings a readily crystallising distil-late of azoveratrole was obtained. After crystallisation from acetic acid this subst,ance melted a t 186O whereas Robinson and Robinson (Zoc. c i t . ) give 182O as the melting point of azoveratrole obtained by the reduction of nitroveratrole with zinc and sodium hydroxide in alcoholic solution. Kauff mann and Kugel (Ber., 1911 44 2388) had previously assigned the melting point 163O t o the substance and it is clear that impurities are removed with difficulty from the product of the direct reduction of nitroveratrole. A mixture of the pure eubstance obtained from azoveratrole and a specimen melting a t 182O previously prepared melted a t 183-186O.Of the two' methods the one now described has the advantage both from the point of view of purity of product and of yield. bleo /'\ I; r i/ \ O J K ~ MeO?jNO=N V O M e -6-Bromoazoxyveratro~e,* A solution of bromine (1.6 grams) in acetic acid (20 c.c.) was gradually added to azoxyveratrole (3 grams) dissolved in acetic acid (50 c.c.). The mixture was cooled in ice water during ten minutes after which water was added and the precipitate collected and crystallised from acetic acid and then from ethyl acetate. The bright yellow needles melted a t 1G0 and were sparingly soluble in alcohol b u t readily so in acetone or benzene: 0.1401 gave 0.0679 AgBr. Br = 20.6. Fruitless attempts were made to prepare a dibromoazoxy-C,,H,,O,N,Br requires Br= 20.2 per cent.veratrole. 6-n7itroazoxyveratroZe (Formula X). A mixture of azoxyveratrole (2.4 grams) and acetic acid (60 c.c.) was treated in the cold with a solution of nitric acid (12 c.c., D 1.42) i n acetic acid (30 c.c.). The azoxy-compound passed into solution and after about ten minutes the nitro-derivative separated in the crystalline condition and in almost quantitative amount. * It has now become necessary to distinguish between the two arornaticnuclei of azoxybenzene and its derivatives. The system suggested is that substituents i n the nucleus attached to the tervalent nitrogen atom should be indicated by simple numerals and those in the other nucleus assumed to be attached to quinquevalent nitrogen by dashed numerals.Such a convention has the advantage that it does not disturb the existing nomenclature but attaches to it a more precise meaning. F 116 ROBINSON AZOXYCATECHOL ETHERS It was collected and recrystallised from acetic acid from which i t separated in bright yellow needles melting sharply a t 185O: 0.1322 gave 13.6 C.C. N at 18O and 744 mm. C,,H,,O,N requires N = 11.6 per cent. The aubstance may also be crystallised from amyl alcohol or ethyl acetate and in the process of crystallisation from either of the three solvents mentioned there always appeared to be two distinct stages. First' bright orange prismatic needles separated, and at a later stage slender yellow needles. The orange crystals retain their appearance when pulverised but the two forms melt alone or when mixed a t 184-185O.No tendency for one form to change into the other was noticed. This substance is sparingly soluble in most organic solvents but dissolves somewhat readily in chloroform even in the cold. The solution in sulphuric acid is momentarily bright red rapidly fading to yellowish-brown. N=11.9. 6 6f-Dirvitroazoxyveratrole (Formula XI). This substance was readily obtained in amount closely corre-sponding with that demanded by theory when either azoxyvera-trole or the mononitro-derivative described above was dissolved in four times its weight of nitric acid (D 1.42). I n either case a clear solution was formed from which the dinitrocompound almost immediately separated. After five minutes water was added and the orange precipitate collected washed with water dried and crystallised from nitrobenzene care being taken to avoid undue prolongation of the necessary heating with the solvent since failure to observe this precaution was found to result in partial decom-position.The substance was obtained in orange leaflets melting a t 287O and very sparingly soluble in solvents: 0.1127 gave 13.0 C.C. N a t 1 3 O and 732 min. C,,H,,O,N requires N= 13'7 per cent. Dinitroazoxyveratrole (1 gram) was dissolved in sulphuric acid (3 grams) and the solution allowed to remain during an hour and a half when the colour changed from brown through violet t o deep indigo-blue. On pouring into water a brick-red pre-cipitate was obtained and this was collected washed dried and crystallised from nitrobenzene.The brilliant red needles were identified by the method of mixed melting points and by careful direct comparison with 2 21-dinitro-4 5 41 51-tetramethoxyazo-benzene (Robinson and Robinson Zoc. c i t . ) . It was not found possible t o obtain an azo-compound by a method similar t o the above from mononitroazoxyveratrole. N=13*4 AND RELATED SUBSTANCES. 117 A zoxypiperonal (Formula 111). A number of comparative experiments were instituted in order to determine the best conditions for the production of the dialdehyde from nitromethylenedioxymandelic acid. The yield could not however be raised to an amount greater than corre-sponds with 25 per cent of that demanded by theory. A solution of 6-nitro-3 4-methylenedioxymandelic acid (5 grams) in aqueous sodium carbonate (10 C.C.of saturated solution) was boiled during two minutes then mixed with a solution of sodium hydroxide (3 C.C. of 40 per cent.) and cautiously heated until a vigorous reaction set in and ammonia was evolved. The reaction was allowed t o proce'ed during one minute without further appli-cation of heat water was then added and the canary-yellow pre-cipitate separated from the deep brownish-red solution ( A ) . The substance was washed with hot water and alcohol and when dry weighed 0.9 gram. It was crystallised from amyl alcohol in which i t is sparingly soluble and again from pyridine being obtained in golden hair-like needles : 0.1159 gave 0.2406 CO and 0.0330 H,O. 0.0848 , 6.1 C.C. N a t 21° and 757 mm.N=8*4. C16H1007N2 requires C = 56.1 ; H = 2.9 ; N = 8.2 per cent, Azoxypiperonal is sparingly soluble in organic solvents and dis-solves in sulphuric acid to a characteristic bright leaf-green solu-tion. If very quickly heated it seems to melt a t about 198O but when the pure substance is heated a t a moderate rate it darkens a t 200° and at about this temperature appears to change into the lactone described below without melting. This changed material gives no colour in sulphuric acid solution and does not melt a t 350O. A very small yield of azoxypiperonal can be obtained by the application of the usual method for the preparation of azoxy-compounds to nitropiperonal in- the following manner. Nitropiperonal (10 grams) was added to a solution of ,sodium methoxide (from 8 grams of sodium) in methyl alcohol (100 c.c.), and the mixture boiled until a test portion diluted with water no longer gave a crystalline precipitate of nitropiperonal but only a flocculent precipitate and it was found to be important that this stage should not be passed.The whole was then poured into water the precipitate collected and extracted with boiling alcohol, and the residue crystallised from amyl alcohol. The slender, yellow needles consisted of azoxypiperonal and showed the same behaviour on heating in sulphuric acid and in the formation of the diphenylhydrazone as the substance obtained from the nitro-methylenedioxymandelic acid. C=56*6; H=3*2 118 ROBINSON AZOXYCATECHOL ETHERS The Diphenyl~~drazone.-This characteristic derivative was obtained from azoxypiperonal in the usual way by condensation with phenylhydrazine in cold acetic acid solution during twelve hours.The substance separated in red needles and was collected and crystallised from ethereal solution by the addition of a few drops of light petroleum (b. p. 50-60O). It formed bright red needles melting a t 203-204O : 0.0811 gave 11.0 C.C. N a t 12O and 742 mm. The substance is rather inclined to undergo decomposition and is readily soluble in most solvents. It may be crystallised froni benzene in glistening red needles but this process to be success-ful must be rapidly manipulated. The alkaline solution R was acidified with hydrochloric acid, and the red precipitate collected washed with boiling alcohol and crystallised from nitrobenzene.The brick-red needles consisted of 4 5 4’ 5’-dimethylenetetraoxyazobenzene-2 2’-dicarboxylic acid (11) and melted a t 270° alone or mixed with a specimen of that acid obtained as described by Robinson and Robinson (loc. cit., p. 1761) but as the melting point is also a decomposition point, the identity was further confirmed by conversion of the substance by the action of nitric acid into 2 2’-dinitro-4 5 41 51-dimethylene-tetraoxyazobenzene. N=16.0. C,8H2,0,N requires N = 16.2 per cent. The Lactone of 3-Hydroxy-5 6 41 5/-a?imethylenetetraoxy-2-phenylindazole-2/-carboxylic cid (Formula VII). This substance is obtained from azoxypiperonal by simply heat-ing to 215O or by boiling the substance with acetic acid or better still with nitrobenzene.From the latter substance the lactone separat’es in clusters of sma,ll colourless needles which do not melt a t 350O: 0.1144 gave 0.2493 CO and 0.0292 H,O. C,,T3806N2 requires C?= 59.3 ; H = 2.5 per cent. The substance is very sparingly soluble in most solvents and gives a colourless solution in sulphuric acid. It exhibits the normal behaviour of a lactone and dissolves in boiling alcoholic potassium hydroxide and the solution remains clear on dilution with water. On acidification the lactone is only gradually repro-duced from the hydroxy-acid. The precipitate is a t first soluble i n alkaline solutions but in course of time becomes insoluble. A small quantity of this indazole derivative was oxidised by half its weight of chromic acid in acetic acid solution.The mixture was gently heated during two minutes and then added to water the C=59-4; H=2.8 AND RELATED SUBSTANCES. 119 precipitate collected and dissolved as far as possible in dilute aqueous sodium hydroxide and the filtered solution acidified. The red flocks were collected and after crystallisation from nitro-benzene the substance was identified as 4 5 4’ 5’-dimethylene-tetraoxyazobenzene-2 21-dicarboxylic acid. This indazole lactone is probably produced in the form of the corresponding hydroxy-acid by the action of sodium hydroxide on nitromethylenedioxymandelic acid. It was repeatedly noticed that the alkaline solution A mentioned above on acidification yielded the red precipitate but after some time a colourless substance also separated from the solution.This product had the properties of the lactone produced from azoxypiperonal. 2-Nitro-4 ; 5 41 5~-dimethylenetetraoxyazo~ybenzene-2~-carboxylic Acid (Formula IV). Azoxypiperonal (1 gram) was added to nitric acid (4 grams, D 1-42) when brown fumes were evolved and a mustard-yellow solid separated; after ten minutes water was added and the pre-cipitate collected. The substance has acidic character and with sodium carbonate forms a fine golden-yellow glistening sodium salt which was crystalIised from hot water and the acid then recovered by acidification. It could now be crystallised from nitrobenzene and obtained in slender mustard-yellow needles which darken a t 320° and melt and decompose indefinitely above 330O: 0.0817 gave 7.4 C.C.N a t 18O and 762 mm. 0.1029 required for neutralisation 0.0116 NaOH whereas this amount of a monobasic acid C,,H,0,N3 requires 0.0110 NaOH. The substance is extremely sparingly soluble in most organic solvents; it suffers no change in boiling sodium carbonate solution, but is attacked by sodium hydroxide with the formation of two new substances. Unfortunately material was lacking f o r a com-plete investigation and the nature of one of the products of the reaction cannot be indicated. The violet claret solution was acidified while hot with hydrochloric acid and the red flocculent precipitate separated by filtration. The filtrate deposited colour-less crystals which have not yet been examined but consist of a substance which dissolves in sodium hydroxide solution with an intense reddish-violet colour.The red precipitate closely resembles dimethylenetetraoxyazobenzenedicarboxylic acid but is not identical with that substance. It is acidic dissolves in sulphuric acid to an intense royal blue solution and on treatment with nitric N=10*8. C,,H,O,N requires N = 11.2 per cent 120 AZOXYCATECHOL ETHERS AND RELATED SUBSTANCES. acid yields 2 2f-dinitro-4 5 4’ 5’-dimethylenetetraoxyazobenzene, but on reduction and condensation of the resultant diamine with phenanthraquinone methylenedioxyphenanthraphemzine was iso-lated. There can therefore be no doubt that the red precipitate consists essentially of 2-nitro-4 5 4’ 5t-dimethyle~ctetrcxoz?/cxzo-benzene-2f-carboxyZic acid. The substance crystallised from hot nit,robenzene in bright red needles melting a t 270O.4 5-Diaminocatechol methylene ether isolated as 2 3-methylene-dioxyphenanthraphenazine was also obtained by the reduction of the nitroazoxycarboxylic acid by means of stannous chloride and hydrochloric acid. O/\CH(O~~e)2. Nitropiperonaldimethy lacetal CH,<*/ 1 NO, \/ This substance was prepared in the hope that i t might be con-vertible into an azoxy-compound by the usual methods and so form a source of azoxypiperonal but nothing of the desired character could be isolated from the products of the reaction between this acetal and sodium or potassium alkyloxides in methyl- or ethyl-alcoholic solution. The acetal was found to be most conveniently prepared by the interesting method discovered by Perkin and employed in the pre-paration of the dimethylacetal of a homologue of nitropiperonal which results from the degradation of cryptopine (T.1916 109, Nitropiperonal (15 grams) dissolved in boiling methyl alcohol (200 c.c.) was treated with nitric acid (5 drops) and after a minute the liquid was allowed t o cool. The acetal crystallised and was collected and a further quantity could be obtained by diluting the mother liquor with water. The substance was well washed with a solution of sodium hydrogen sulphite and crystallised from methyl alcohol. The almost colourless flat needles melted a t 69O, and are rather readily soluble in organic solvents with the excep-tion of light petroleum: 911). 0-1514 gave 7.8 C.C. N at 1 8 O and 742 mm. C,,H,lO,N requires N = 5.8 per cent.The substance does not exhibit an aldehydic character and gives no indigatin with acetone and sodium hydroxide. It is readily hydrolysed to nitropiperonal and methyl alcohol (acetate) by means of acetic acid and a drop of sulphuric acid. All attempts t o produce azoxy-compounds resulted in the hydrolysis of the methyl en ediox y-gr oup. N=5*9 EVIDENCE OF THE Axox yveratraldehyde, EXISTENCE IN MALT ETC. 121 The behaviour of 6-nit.ro-3 4-dimethoxymandelic acid is entirely similar to that of the methylenedioxy-analogue and the reaction with sodium hydroxide was carried out in an identical manner. The alkaline filtrate from the yellow precipitate was acidified with hydrochloric acid and the red substance collected and crystal-iised from nitrobenzene.Beetle-green crystals were obtained and these melted a t 274O alone or mixed with a specimen of 4 5 4’ 5’-tetramethoxyazobenzene-2 21-dicarboxylic acid (Robinson and Robinson Zoc. cit.). Azoxyveratraldehyde is more readily soluble than azoxy-piperonal and may be crystallised from ethyl alcohol but better from amyl alcohol. It is obtained in bright yellow slender needles melting a t 1 8 5 O : 0.0480 gave 3.0 C.C. N at 15O and 760 mm. The substance dissolves in sulphuric acid to an emerald green solution. On boiling with nitrobenzene or acetic acid i t is con-verted into a colourless substance which crystallises from acetic acid in well-formed colourless needles melting at 257O. I n all respects this substance resembles the previously described indazole derivative from azoxypiperonal and like it gives no coloar in sulphuric acid shows the behaviour of a lactone with alcoholic potassium hydroxide and on subsequent acidification and without doubt is the lactone of a hydroxytetramethoxyphenylindazoIe-carboxylic acid. N = 7 * 5 . ClsHlsO,N requires N = 7.5 per cent. UNIVERSITIES OF SYDNEY AND LIVERPOOL. [Received January 3 01 h 1 9 1 7.

ISSN:0368-1645    

DOI:10.1039/CT9171100109

出版商:RSC    

年代:1917

数据来源: RSC

摘要:

EVIDENCE OF THE EXISTENCE IN MALT ETC. 121 XITI.-E,vidence of the Existence in Malt of an Enzyme Hydrolysing the Furfkroids" o f Barley. By JULIAN LEVETT BAKER and HENRY FRANCIS EVERARD HULTON. 1.r has been shown by Tollens and Glaubitz ( J . Landw. 1897 106) and by Cross and Bevan (Ber. 1894 27 1064 2604) that barley * The discussion of these substances is made difficult by the lack of uniformity in their nomenclature the expressions pentosan and furfuroid having been used indiscriminately. Throughout this work no pentosans or pentoses have been actually isolated furfural having been estimated as 122 BAKER AND HULTON EVIDENCE OF THE EXISTENCE IN MALT contains 9 to 10 per cent. of furfuroids. The first-named authors (Zoc. cit.) estimated the amount of furfuroids in a weighed portion of barley and in the malt derived from the same barley and con-cluded that the furfuroids in barley in no way diminished during the germination process (see also Cross and Bevan Zoc.c i t . ; de Chalmot Amer. Chem. J. 1894 16 218; ?7. Landto. 1896 188). Tollens ( J . Fed. Inst. Brewing 1898 4 445) considers that during the malting process the furfuroids do not take part in respiration, and conjectures that by the respiration of the germinating barley fresh amounts of furfuroids or oxidation products which yield furfural (probably derived from starch) may be formed. This he thinks must remain a moot point for the increase is so small that it may be due to experimental errors. Moreover the possibility is also presented although Tollens regards it as a slight probability, that on the one hand furfuroids are regenerated from sugar or starch and on the other that they have taken part in respira-tion so that the two compensate each other.Windisch and Van Waveren (Wochensch. Brau. 1909 26 581) have noted that during the malting process the amount of fur-furoids soluble in water present in the germinating barley pro-gressively -increases. I n one experiment (Zoc. cit.) Tollens found 9.26 per cent. of furfuroids in a sample of barley and 9.88 per cent. in the malt made from it. As he obtained a yield of dry malt from dry barley of 95.6 per cent. it would appear that the malt still retained its rootlets or the yield would not have exceeded 91 per cent. This point is of importance as we find malt rootlets contain on the average nearly twice as much furfuroids as barley.Cross ( J . Fed. Inst. Brewing 1897 3 2 ) obtained a yield of 5.5 per cent. of furfural from barley and 5-3 per cent. from malt but whether this malt was from the same barley is not stated. The polysaccharides a- and P-amylan described by O’Sullivan (T. 1882 41 24) and by Brown and Millar (Trans. Guinness Res. Lab. 1906 312) a d the galactoxylan obtained by Lintner and Dull from barley (Zeitwh. angew. Chem. 1891 538) are also of interest’ in connexion with the cereal furfuroids. During the course of this investigation furfnral was estimated by a process described by us (Analyst 1916 41 244) which is a modification of Flohil’s method (Chew. Weekblaad 1910 7 1057) as elaborated by Eynon and Lane (Analyst 1912 37 41) in measure of their amount.As however there are soluble as well as insoluble pentosans we have decided to employ the general term “ furfuroid,” originally adopted by Cross and Bevan as meaning any substance yielding considerable quantities of furfura,l on distillation with hydrochloric acid OF AN ENZYME HYDROLYSING THE FURFUROIDS OF BARLEY. 123 which advantage is taken of the reducing action of furfural on Fehling’s solution under standard conditions. The Fehling’s solution and furfural are heated in a flask fitted with an upright condenser in a boiling-water bath for forty minutes. Under these conditions spontaneous reduction of Fehling’s solution falls from 20 t o 4 milligrams of cuprous oxide (Analyst Zoc. c i t . ) . We have found the method to be one susceptible of great accuracy and much to be preferred t o the phenylhydrazine or phloroglucinol reactions usually employed.Since our early experiments confirmed Tollens in finding a slightly increased percentage of furfural in malt free from root-lets as compared with the original barley we thought i t of interest to follow the distribution of furfuroids found in different parts of the barley and malt corn the more so as we hoped t o throw some light on the mechanism of the formation of furfuroid from non-furfuroid matter during germination. The following estimations of furfuroids in the entire corn were made on three samples of barley and the corresponding malts freed from their rootlets : Grams of furfural obtained from Grams of dry malt yielded by 100 Grams of furfural obtained from the English.Oregon. Californian. 100 grams of dry barley ............ 4-93 5.87 6.05 grams of dry barley .................. 90.7 91.9 86.8 above weight of malt ............... 5.63 6.07 5.87 I n the case of the English and Oregon malt the furfuroids are in excess of those found in the corresponding weights of their original barleys notwithstanding the removal of some 3-5 per cent. of rootlets which themselves yield 9 per cent. of furfural whilst the additional furfural matter formed during the germination of the Californian barley has just failed to compensate for that removed in the rootlets. It’ may therefore be inferred that during germination a small but distinct formation of furfuroids occurs.The next point investigated was the relative distribution of furfuroids in the barley and malt corns the following values for furfural being obtained : Per cent. of furfural on dry weight. Entire barley corn (Oregon) .................. 5-87 Excised embryos before germination ...... 4.68 Young plumules germinated in the dark ... 5-74 Rootlets (culms) from malt ..................... 9.14 Malt husks (brewers’ grains) .................. 20-5 Here it will be seen that the furfuroid content of the embryo, which constitutes about 3 per cent. of the barley corn by weight, is appreciably lower whilst the rootlets and husks of the malt are much higher than in the entire barley 124 BAKER AND HULTON EVIDENCE OF THE EXISTENCE IN MALT The fact that the rootlets of the malt are so much richer in furfuroids than the embryos suggests that soluble furfuroids play their part in the development of the young plant.The question naturally arises as t o how this furfuroid material in the rootlets has been elaborated since at some time during germination fur-furoid matter must have become soluble to be conveyed through the embryo to form part of the cellular structure of the rootlet unless the furfuroid matter of the roots was formed entirely from diffusible sugars such as maltose or sucrose. We thought some light might be thrown on this point by germinating embryos on a non-furfuroid medium such as sucrose to ascertain if they possessed the capacity of forming furfuroid material from such a substrate or in other words a C carbohydrate from a biose.Tollens (Zoc. cit.) was aware of this possibility and suggested that an atom of carbon was removed from a hexose during respiration. Our mode of experiment was to soak barley in water for a few hours then excise the embryos and grow them in Petri dishes on sterilised sand moistened with 5 per cent. sucrose solution containing a trace of asparagine. The germination was conducted in the dark any disturbing factors arising from possible photo-synthesis being thus avoided. After €our days’ growth the germinated embryos which grew quite freely were withdrawn from the sand carefully washed, dried in a vacuum weighed and the furfuroids in them estimated. Original ungerminated barley embryos. Germinated embryos. Weight per 1000 (dry) ... 1.10 grams.1-6 grams. Per cent. of furfural on dry Furfural per 1000 embryos 0.05 gram 0.10 gram Increase in weight per cent. 44 weight ........................ 4-68 6-41 The barley embryos may be considered to consist of two kinds of matter namely furfuroid (10 per cent.) and non-furfuroid (90 per cent.). On being allowed to germinate on sucrose-sand the dry weight of each embryo is increased by about 44 per cent., whilst the furfuroid per embryo has been doubled and the pro-portion of furfuroid per cent. on total matter has been increased from 4.68 to 6.4. Since the results show there is an increase in weight and in furfuroid content during germination it may be concluded that mcrose has been absorbed and in part converted into furfuroids. There is however another possible explanation of the phenomenon, namely the formation of new furfuroids from the 90 per cent.of non-furfuroids present in the embryo before germination. Thus whilst sucrose is being used by the embryo to form new furfuroi OF AN ENZYME HYDROLYSINQ THE FURFUROIDS OF BARLEY. 125 tissue some of the originai non-furfuroids in the embryo under the stimulus of active growth are producing furfuroids. The obvious extension of this experiment was to ascertain if there were a similar production of furfuroids in the embryo when growing naturally attached to its. own endosperm. A sufficient number of corns were soaked in water for sixty hours and then placed between layers of clean damp linen and germinated in the dark for six days. The young plantlets were then excised from their endosperms dried in a vacuum weighed and the furfuroid matter estimated.The furfuroids were estimated in these residual endosperms from which the embryos had been removed for on consideration it will be evident that unless there is a formation of new furfuroids any gain in the amount found in the embryos should balance the loss sustained by the endosperms. The following figures show that there is no evidence of the formation of new furfuroids: Furfural per 1000 barley corns ....................................... 2-22 grams. Y , embryos after germination .................. 0.23 ), 9 ) residual endosperms after germination ... 1.87 ,, Now 0.23 + 1.87 = 2.10 which is an amount slightly less than the furfural in the original barley namely 2.22 grams.It will thus be seen that the embryo when grown naturally, prefers to use the furfuroids of its own endosperm rather than elaborate such matter from sugar which as we have previously shown i t can do when grown on sucrose-sand. Such a transference of furfuroids suggests the probability of enzymic activity involving the hydrolysis of insoluble furfuroids and the passage of the soluble products through the epithelial layer of the embryo. We can find no references in the literature to an enzyme capable of hydrolysing an insoluble furfuroid; in fact E. F. Armstrong in '' The Simple Carbohydrates and the Glucosides " (Longmans, 1910) on p. 37 denies the existence of such an enzyme. We thought it of interest to estimate the water-soluble furfural-yielding material in malt as compared with barley for if the furfuroids of barley are subject to enzymic hydrolysis during germination i t is to be anticipated that the amount of such soluble products will be greater in the malt'.Barley and the malt made from i t were finely ground and extracted for four hours with cold distilled water the furfural obtainable from the clear filtrate being estimated. The results obtained are given in the following table the furfural expressed (1) as a percentage on the original total material extracted ( 2 ) a 126 BAKER AND HULTON EVIDENCE OF THE EXISTENCE IN MALT a percentage of the tot,al furfural and (3) as a percentage of the total matter eoluble in water : Barley. Malt. h h ,- \ / - -. Cali- Cali -fornian.English. Oregon. fornian. English. Oregon. Total furfural per cent. on dry matter ...... 4.93 5.87 6.05 6.21 6-61 6.77 Soluble furfural per cent. on dry matter 0.28 0.19 0.20 0-96 0.81 0.85 Soluble furfural per cent. on total fur-Soluble furfural per cent. on total soluble fural .................. 5.6 3.2 3.3 15.5 12.3 13.0 matter ............... 3-4 2.2 2.2 4.5 3-8 4.6 The anticipated formation of soluble furfuroids has occurred, since only from 3 to 5 per cent. of the total furfuroid matter in barley is soluble whilst from 13 to 16 per cent. of that in malt dissolves in cold water. The fact (shown in the last line of the table) that the weight of furfural expressed as a percentage on total matter soluble in water is slightly higher in malt than barley whilst the water-soluble matter in malt is more than three times as great as in barley shows clearly how marked has been the formation of soluble furfuroids during malting and also indicates that the formation of the soluble furfuroids has more than kept pace with the forma-tion of other sugars during germination.As a quantitative measure of the activity of the enzyme we measured the furfuroid matter passing into solution from barley when acted on by the active enzymes present in germinating malt -a stage at which it was t o be expected that a " pentosase " would be a t a maximum state of activity. Control experiments for estimating the already existing soluble furfuroids in the same malt and barley were made separately alongside the digestion of the mixture in order that the amount so passing into solution could be deducted from the total found in the mixture and thus a measure obtained of the furfuroids passing into solution as a result of the action of green malt enzymes on insoluble furfuroids.Barley and green malt were digested separately and in admixture in the presence of toluene for sixty-eight hours a t 35O. A t the end of this period the digestions were filtered and the furfural obtained from the filtrates was estimated. The experiments were carried out with Californian and White Oregon barleys the follow-ing results being obtained OE" AN ENZYME HYDROLYSINQ THE FURFUROIDS OF BARLEY. 127 Oregon. Californian. A f- I v-Mixture of Mixture of Green barlev and Green barley and Barley. Weight of material Volume of added responding with 17.64 Dry weight of ori-ginal material cor-100 C.C.of filtrate (grams) ............... Furfural obtained from filtrate per 100 grams of ori-ginal dry matter (grams) ............ 0.9 Furfural calculated per 100 grams of barley after cor-recting for malt present in mixture Increase due to en-zyme action. Fur-used (grams) ...... 40 water (c.c.) ......... 200 I (grams) ............ 1.11 fural (grams) ...... 0.63 I n both cases there is malt. malt. Barley. malt. mdt. 40 20+20 50 50 25+25 200 200 250 250 250 1.91 1.45 0.51 1.06 0.89 - - 0.78 - -- 0.27 - - -an appreciable increase in the amount of soluble furfuroid matter obtained from barley in the presence of the green malt as compared with that dissolved by water alone.The green malt from the Oregon barley proved the more active, this being probably due t o the fact that it had remained on the malting floor for ten days whilst the Californian was only four days old. We think these results may be regarded as evidence in support of the production of soluble furfuroid material from insoluble furfuroid material by the action of a " pentosase" con-tained in the green malt. extract. It may be urged that the increase in furfuroid content of barley when acted on by green malt is not necessarily due to a " pentosase," but t o the aqueous extraction of furfuroid material otherwise insoluble. This might arise from the dissolution of the cellular membranes or walls enclosing soluble furfuroid material.Arguments in favour of this alternative explanation would be weakened if it could be proved that insoluble furfuroids could be rendered soluble when using a substrate previously heated in such a manner as t o liberate any furfuroids so enclosed. It is well known that when an aqueous infusion of malt is poured into an excess of strong alcohol a precipitate containing amylase separates. It appeared likely that such a precipitate would also contain the " pentosase " just alluded to and we accord-ingly prepared some from a sample of green malt which ha 128 BAKER AND IIULTON EVIDENCE OF THE EXISTENCE IN MALT germinated for six days on the floors and presumably contained the enzyme in an active condition. The substrate which we selected for this enzyme to work on was malt grains a material rich in furfuroids.The mash-tun grains were purified by digest-ing in the first place with diastase to remove any adhering starch followed by treatment with acid and alkali (1.25 per cent.) in the cold. These grains were then acted on by the aqueous solu-tion of the enzymes for three days at 30° in the presence of a little toluene filtered and the furfural obtainable from the filtrate estimated. A control experiment in which a portion of the boiled enzyme preparation was digested was carried out alongside. This is necessary since the alcoholic precipitate of the green malt’ extract carries down with i t a certain amount of furfural-yielding substances. The original sample of dried grains yielded 20.5 per cent. of furfural and when subjected to the action of the precipitated enzymes the hydrolysed soluble products formed as the result of the action yielded 2.2 per cent.of furfural; that is t o say 10.7 per cent. of the total furfuroids in the grains were converted into products rendered soluble by the action of a furfuroid-splitting enzyme. Here there can be no suggestion of the extraction of soluble furfuroids due to cytase action alluded to’ above since the grains have already been subjected to treatment which would result in their liberation and removal. I n order to obtain still further confirmatory evidence of “ pentosase ” action the following experiment was made in which the sugars formed as a result of its action on dried grains were estimated by their reducing action on Fehling’s solution.A quantity of green (English) malt grown for ten days on the malting floor was extracted with four times its weight of dis-tilled water for three hours at 1 5 O . The clear filtrate was allowed to act on brewers’ grains which had been purified in the manner previously described the digestions being made in the presence of toluene for ninety hours a t 30°. Controls in which corresponding volumes of the boiled malt extract were employed were also carried out alongside. The reducing sugars in the filtrates were estimated a t the end of the digestion period by Brown Morris and Millar’s method (T. 1897 71 72) and the weight of cupric oxide obtained (corrected for the reducing power of the malt extract in the control) calculated into xylose by Daish’s tables ( J .Agric. Sci., 1914 6 258). The following results were obtained from two such digestions the weight of dried grains substrate (1.5 grams) bein OF AN ENZYME HYDROLYSING THE FURFUROIDS OF BARLEY. 129 the same in both cases but the volume of malt extract in the second being double that used in the first: I. 11. Volume of malt extract used ............... 25 C.C. 50 C.C. Weight of.xylose obtained from 1-5 grams of grains (corrected for reducing Xylose per cent. on pentosan in the power of malt extract) ..................... 0.18 0.36 Xylose per cent. on grains .................. 12.2 24.1 grains .......................................... 34 67 The original sample of grains yielded 20.5 per cent. of furfural, and multiplying by the customary factor 1.75 this equals 35.8 per cent.of pentosan (furfuroids). Not only has the " pentosase " in the green malt extract produced a considerable yield of reducing sugar from the grains but the amount produced is proportional to the volume of enzyme solution employed. Summary and Conclusions. (1) Estimations of furfural yielded by barley and the malt made from it afforded evidence of a small but distinct production of furfuroid from non-furfuroid matter during the malting process. (2) Embryos excised from barley when grown in the dark on sucrose increased both in weight and furfuroid content. It is probable t h a t the new furfuroid matter formed was derived from the sucrose substrate. (3) Barley embryos when grown in a natural state attached t o their own endosperms showed on subsequent excision an increase in furfuroid content corresponding with the loss of the same material sustained by the residual endosperms.This may be taken as evidence of an enzyme capable of hydrolysing furfuroids in the non-embryo portion of the grain and of their transference in a soluble condition t o the embryos in a manner analogous to t h a t occurring under the influence of diastase in the starchy portion of the endosperm during germination. (4) I n further experiments designed to measure quantitatively the activity OP such a furfuroid-hydrolysing enzyme digestion in vitro of green malt and barley showed t h a t a portion of the insoluble furfuroids in barley became soluble as the result of enzymic activity of the green malt. (5) Using purified malt husks as a substrate it is shown that 10 per cent. of their insoluble furfuroids are hydrolysed to soluble furfural-yielding substances when acted on a t 30° by the enzymes separated by alcohol from green malt. VOL. CXT. 130 WHEELER “ STEPPED ” IGNITION. (6) An aqueous extract of green malt when allowed to act on brewers’ grains produces reducing sugars (pentose) proportionate in amount to the volume of the malt extract employed. We desire to express our thanks to Miss A. Crawley for assist-ance in part of the experimental work recorded in this paper. THE LABORATORP, THE STAG BREWERY, PIMLICO S.W. [Received February 5th 19 17.

ISSN:0368-1645    

DOI:10.1039/CT9171100121

出版商:RSC    

年代:1917

数据来源: RSC

摘要:

130 WHEELER “ STEPPED ” IGNITION. XIV.-“ Stepped ” Ignition. By RICHARD VERNON WHEELER. DURING researches on the electrical ignition of gases W. M. Thorn-ton has observed certain discontinuities to which he has applied the term “steps,” and on which he bases a theory regarding the manner in which the ignition of inflammable mixtures of gases in general is effected. The steps were first recorded when determining the effect of change in the composition of mixtures of ethane and air on their ignition by condenser discharge sparks (Proc. Roy. SOC. 1914 [ A ] , 91 18). They are also stated by Thornton to occur when ignition is by the impulsive electrical discharge either (1) when the pro-portions of a combustible gas (for example methane) mixed with air are varied the pressure being maintained constant (Proc.Roy. SOC. 1916 [A] 92 388) or (2) with a given mixture of com-bustible gas and air when the pressure is varied (Brit. ASSOC. 1916, Section C; Colliery Guardian 1916 112 503). Sastry (T. 1916 109 523) working a t the Home Office Experi-mental Station was unable to confirm the former of the two observations respecting ignition by the impulsive electrical dis-charge in the case either of methane or of hydrogen. The remarkable nature of Thornton’s results and the import-ance of the theories to which they lead demands that anyone working on similar problems should carefully check them. This I have attempted to do in the case especially of mixtures of methane and air. The steps observed by Thornton when the percentage of methane in air was varied and ignition was by tlhe impulsive electrical dis-charge were ill-defined and are stated to have occurred only whe WHEELER “ STEPPED ” IGNITION.131 the sparking electrodes were unclean. Their existence is therefore doubtful. Using a method of experiment apparently similar to Thornton’s I have been unable to detect any discontinuity, although the curve has been traced over a wide range half-a-dozen times or more. Incidentally it may be stated that no discontinuity has been observed with mixtures of air with hydrogen or with any one of the gaseous paraffin hydrocarbons the only gases with which experiments were made. An account of this work is reserved for a future communication. I propose for the present to confine myself to an examination of the more striking discontinuities recorded by Thornton when a 9.5 per cent.mixture of methane and air was ignited a t different pressures by the impulsive electrical discharge. A curve representing the results of Thornton’s experiments (Zoc. cit.) is shown in Fig. 1 (the curve on the right-hand side of the diagram). The (‘ igniting-currents ” recorded are those currents passing through the primary circuit of an induction coil which, when broken gave secondary discharges just capable of igniting the mixture 132 WHEELER ‘‘ STEPPED ” IGNITlON. My own results are also shown in Fig. 1. The mixture of methane and air contained 9.51 per cent. of methane (by analysis) in the case of curves A and B and 9.52 per cent. in the case of curve C. A different explosion-vessel was used for each curve the spark-gaps of which differed slightly one from another but were approximately 1 mm.in each case. Each curve is hyperbolic and there is no sign of discontinuity. It would seem therefore that the production of (‘ stepped igni-tion,” such as has been recorded by Thornton requires some con-dition of experiment which I have been unable to reproduce-or have been careful to exclude. A detailed description of my experimental conditions is therefore given. E x P E R I M E N T A L . If the vibrating contact in the primary circuit of an induction coil is held closed and the circuit is suddenly broken a single disruptive discharge takes place at a spark-gap in the secondary circuit. With a given spark-gap and a given rate of break of the primary circuit the voltage of the secondary discharge is proportional to the primary current.The relative ease of ignition of different gaseous mixtures or of the same mixture a t different pressures can thus be measured by measuring the least current passing in the primary. circuit of a given induction coil which when broken at a constant rate gives a discharge or ((spark’ a t a fixed spark-gap just capable of igniting the mixtures. It will be seen that to ensure truly relative results it is essential (1) that the spark-gap in the explosion-vessel should be fixed and incapable of inadvertent or unobserved alteration and (2) that no variation should occur in the rate of break of the primary circuit. I n Fig. 2 is shown the form of explosion vessel used for the experiments described in this paper.It consists of a globe of stout glass of about 75 C.C. capacity with fixed electrodes of stout platinum wire fused in. The electrodes reach to the centre of the vessel and are covered with glass t o within 1 mm. of their ends, which are sharpened to fine points. A three-way tap serves to make connexion with (1) a gas-holder and mercury manometer and (2) a vacuum pump. Fig. 3 is a photograph of the arrangement for ensuring an unvarying rate of break of. the primary circuit. The circuit is completed when the rod A touches the flat steel spring B remains established while the turntable revolves and is suddenly broke [ T o ,face p. 132. 133 WHEELER “ STEPPED ” IGNITION. as soon as the rod slips off the end of the spring.The turntable is driven by an electric motor geared down to a slow speed so that a break of circuit in the primary of the induction coil occurs every two seconds. A condenser of 0.25 microfarad is placed across the break to’ minimise sparking at the contacts. The coil used was an “ 8-inch ” X-ray coil. Current was obtained from a battery of accumulators a t 30 volts and was measured (regulation being made by a sliding rheostat) with “Weston ” ammeters. The gas-mixtures were stored over glycerol and water in glass gas-holders and were analysed before use. The same supply (con-taining 9-51 per cent. of methane) was used for the experiments FIG. 2. recorded in curves 9 and B ; the supply used for curve G con-tained 9.52 per cent.of methane. The gas was prepared by purify-ing and liquefying firedamp obtained compressed in cylinders, from a coal mine in South Wales and contained 99.8 per cent. of methane (CIA on explosion analysis 2.00). As already stated three different explosion vessels were used one for each curve the spark-gap in each case being about 1 mm. The method of experiment was that of tria<l and error. The explosion-vessel was thoroughly exhausted of air and some of the gas-mixture admitted until the pressure as read on the mercury manometer was that required. An arbitrary current was estab-lished in the primary circuit of the induction coil and te 134 WHEELER “ STEPPED ” IGNITION. secondary discharges passed a t the spark-gap by setting the revolv-ing contact in motion.I f ignition did not take place before ten discharges had passed the explosion-vessel was exhausted a fresh charge of gas-mixture introduced and a higher current tried; and so on until the limiting current was fixed a t each pressure within 0.01 ampere for currents below 3 amperes and within 0.1 ampere for currents above that figure. Each point on each curve was checked three or four times and no discrepancies were observed. A t pressures as low as 50 mm. mercury it was difficult to decide by direct observation whether ignition took place or not the glow of the discharge masking that of the ignited gases; a contraction in volume occurred a t 50 mm. pressure (curve A ) with an igniting-current of about 10 amperes. My friend Mr. Allan Greenwell has been good enough to make a mathematical analysis of curve A the results of which are as appended.MATHEMATICAL. (By ALLAN GREENWELL.) The curve obtained by plotting igniting-currents as ordinates against pressures as abscissae is remarkably smooth and suggests that it follows a definite law. Taking the experimental determinations a t pressures of 1 2 3, 5 and 7 I ‘ hundred mm.” of mercury as recorded by curve -4 and assuming that the curve-is a conic the following empirical equa-tion is obtained: 2 2 - 11.6852 + 4.1867~2- 5 3 . 3 7 3 ~ + 35.5329 - 77.865 =O. From this formula it can be shown that the transverse axis of the curve is inclined to the axis of abscism a t an angle of +47O33*75/. By rotating the axes of co-ordinates through this angle so that they are brought into parallel with the axes of the curve the equation becomes : From this equation it is seen that the curve is a hyperbola the semi-axes of which are 2.132 and 2.469 respectively the centre being situated a t the point x= + 1.157 y= -0.895 referred to the new axes or x= + 1.444 y = + 0.2476 referred to the original axes.By calculation the curve cuts the axis of abscissz and the axis of ordinates a t x= + 16.425 and y= + 14.07 respectively and the transverse axis of the curve cuts the axis of abscissae a t x= + 1’2176 135 WHEELER " STEPPED " IGNITION. The following table gives the observed and calculat,ed values of a and y : Relative igniting currents. Pressures. (Mm. of mercury). (2). 100 .................. 150 .................. 200 ..................220 .................. 250 .................. 300 .................. 350 .................. 400 .................. 450 .................. 500 .................. 550 .................. 600 .................. 6 50 .................. 700 .................. 750 .................. (Amperes). (?/I- - Observed. Calculated. 7.20 7.20 4.60 4.75 3.15 3.15 2.65 2-72 2.22 2.25 1-72 1.72 1.38 1.39 1.12 1-16 0.95 1.00 0.87 0.87 0.77 0.77 0.68 0.69 0.60 0.62 0-56 0.56 0.52 0.51 The fact of the hyperbola cutting the axes of co-ordinates has been very puzzling. Assuming that the experimental work is accurate and that the numerical quantities represent the ex-perimental determinations truly that is to say that they quanti-tatively represent respectively the igniting power of the current and the state of compression of the gaseous mixture a t the exact moment and locus of ignition then the curve cannot cut the axes.For there cannot be ignition a t 0 mm. pressure and at no pressure (under the conditions of the experiments) can the igniting current be less than zero. The following argument is suggested as a clue to a possible explanation of the apparent anomaly. The curve is plotted to rectangular axes which assumes that the quantities represented by measurements along the axes are absolutely independent of each other. The question is Does this condition prevail in the present case ? (1) I f the current (y) is increased without intentionally chang-ing the pressure (x) a change of pressure may still take place, automatically due to the energy of the spark.(2) If the pressure is increased without intentionally changing the current a change in the activity of the spark may take place due to a change in the resistance of the spark-gap caused by the change of the density of the intervening medium. I n either of these hypothetical cases the measurements to be represented by x and y would not be altogether independent of each other. An inspection of the accompanying diagram (Fig. 4) will sho 136 WHEELER “ STEPPED ” IGNITION. that in order to prevent the curve cutting the axes of co-ordinates, these axes must be parallel to the asymptotes of the curve and the curve must lie wholly within one “quadrant.” Using the same origin but employing inclined axes parallel to the asymptotes of the hyperbola then considering any point on the curve the new inclined ordinate (y’) will represent the real igniting power compared with the old rectangular ordinate (9) which represents the recorded igniting current.I n the same manner the inclined abscissa (2’) will show the real compared with the recorded pressure (x). pressure 1 -x - - -y 1 2 3 4 5 G ’ i S Pressures ‘‘ hundred mm. ” mercury. Calculated point’s on the curve where they differ appreciably from the observed points are shown as crosses. The relations between XI y’ and z y are given by the follow-ing equations where + is the angle between the asymptotes and 8 is the angle of inclination of the transverse axis of the hyper-bola to the horizontal axis of abscissz?: 2’ = (I2 - y cot (+/2 + 6)][cos (+/a - 0) - cot + .sin($+ - 6 ) ] 9’ = [y + x tan (+/a - 6)][sin (+/2 + 8) + cot + . cos(+/2 + O,]. I n the case under consideration q5 = 98O21.68’ and 8 =47O33-75‘ WHEELER “ STEPPED ” IGNITION. 137 From these equat,ions the values of XI y‘ have been calculated for the typical points on the curve the rectangular co-ordinates of which were used for calculating the empirical equation of the curve : (x). (Y 1- (x’). (Y‘b 1.0 7.20 1.86 7.30 2.0 3.15 2-38 3.24 3.0 1.72 3.21 1.82 5.0 0-87 5.12 1.02 7.0 0.56 7.09 0.76 The asymptotes of the hyperbola cut the inclined axes (OX’, OY’) at distances from the origin equal respectively t o [ p sin (+/a + e) - q cos (+/a + e)] cosec $.[ p sin (+/z - 0) + p cos (+/a - O)] cmec +. where p and q are the co-ordinates (rectangular axes) of the centre of the hyperbola. I n the present case p = 1.444 and q=0*2476. Substituting numerical values the expressions become respectively 1.479 and 0.2914. Then taking the inclined co-ordinates of any point on the curve and deducting from the abscissa the value 1.479 and from the ordinate the value 0.2914 and multiplying the differences it is found that the product is always a constant and equal approximately to 2.66. The value of the constant (2.66) is equal to a2+ b 2 / 4 where a and b are respectively the semi-transverse and semi-conjugate axes of the hyperbola. It should be borne in mind that throughout the present in-vestigation the dimensions of the hyperbola have not been changed or its position with regard t o the origin altered.The only varia-tions that have been made have been in regard to the inclination of the axes of co-ordinates and their included angle. The general conclusions suggested by this mathematical analysis of curve A are as follow: (1) The quantities represented by the observations of the igniting-current and the degree of compression are mutually involved. (2) The real quantities as distinguished from the recorded quantities may be represented by employing inclined axes parallel to the asymptotes of the hyperbola the position of the origin remaining the same. (3) The distance parallel to the axis OX’ between the axis OY’ and the relative asymptote represents the real value of the minimum pressure a t which ignition can be obtained (under the experimental conditions) with any current. The distance parallel and VOL. CXI. 138 SEYLER AND LLOYD: to the axis Or’ between the axis OX‘ and the relative asymptote represents the real value of the minimum current which can pro-duce ignition (under the experimental conditions) with any degree of compression. (4) The product obtained by multiplying the real value of the pressure less the minimum pressure by the real value of the igniting current less the minimum igniting current is constant. ESKMEALS, CUMBERLAND. [Received December 27th 1916.

ISSN:0368-1645    

DOI:10.1039/CT9171100130

出版商:RSC    

年代:1917

数据来源: RSC

摘要:

138 SEYLER AND LLOYD: XV.-Studies of the Carbonates. Part 11. Hydro-lysis o f Sodium Carbonate and Bicarbonate and the Ionisation Constants of Carbonic Acid. By CLARENCE ARTHUR SEYLER and PERCY VIVIAN LLOYD. THE ionisation constant of carbonic acid in the equilibrium equa-tion [HI x [HCO,] =k2[H2C03] is well established by the experi-ments of Walker and Cormack and has the value 3 * 0 4 ~ 1 0 - ~ a t 18O. The value of the second ionisation constant in the equation [HI x [CO,] =k,[HCT03] is however lstill uncertain even after correction of the value deduced by Bodlander (Zeitsch. physilcal. Chem. 1900 35 32) from the experiments of Shields (ibid. 1893, 12 167) which was first made by McCoy (Amer. Chem. J. 1903, 29 437). This is due t o the fact that the value of k found experimentally varies with the concentration of the carbonate.Two methods have been used namely: (1) That of McCoy (Zoc. cit.) who determined the ratio (2) That used by Shields (Zoc. cit.) who determined the ratio 5 = - IHW1 [OH] by experiments on the hydrolysis of ethyl k [C%l acetate and by Auerbach and Pick (Arb. Kais. Gesundheitsamt, 1911 38 II) who determined the hydrogen concentration colori-metrically. increase decidedly with dilution but not in the same ratio as would be k In both cases the values of -t and 5 A3 7% expected if k were really subject t o variation. This can scarcely be thO case so that the cause of the apparent variation must b STUDIES OF THE CARBONATES. PART TI. 139 sought i n the degree of ionisation of the carbonate and bicarbonate.c N f ~ H C 0 3 and Let k be the apparent value of the ratio -CNa&Os [H,co3] k,l of the ratio 'h'aHC03. [OH]. Cln.a2c0:< The values of [H2C0,] and [OH] do not involve any ionisation correction the latter having been directly determined either by the hydrolysis of ethyl acetate or by a colorimetric method; but the values of C N ~ ~ I C O and C(NaaCO:2 require to be multiplied by tho degree of ionisation of From this it is evident a t eIy. Attempts have b,een the values of a and the respective salts a and fl. Hence k f and (2) '3 = ktE i. k , that k and /cci will not increase proportion-made by all workers to form estimates of p. S t i egli t z (Car iz eg i e Ins t . Pu b 1 i CQ t .i o i l , No. 107) assumes the dissociation of sodium bicarbonate to be the same as t h a t of sodium acetate.This is probably a fair approxim-ation. The ionisation of the carbonate has be'en assumed to be the same as t h a t of sodium sulphate. This is more doubtful. Stieglitz assumes f o r a concentration of 100 x 10-3 fl=O*687 and for 300 x 10-3 p=0*584. These are no doubt too high since Harkins and Bray show ( J . Amer. Chein. Soc. 1911 33 1864) that ions such as NaSO exist in concentrated solutions. Bray estimates for c = 100 x 10-3 p = 0.598 and for c = 1000 x 10-3 p=0*420. Auerbach and Pick simply assume a value p=0*60 for c=95 x 10-3. It appeared to us t h a t the problem could be attacked in another way. If we have good determinations of k, and kdat corresponding concentrations it is evident that we can calculate a by eliminating k from equations (1) and (a) namely, k k kt" * k, a = - 2, Were k is well established.Most workers have taken too high For 2 5 O McCoy used 1~,,=1*2 x 10-14 Auerbach The later determinations of Kanolt (Cctrjzegie Inst. f'ublicatioiz, Auerbach and Pick have recalculated Shields's values for k d as a value f o r k,. and Pick k,= 1-05 x 10-14. No. 63) give decidedly lower figures namely 0.82 x 10-14 a t 25O. follows : c (equivalents). kd. 380.0 x 8.16 x lo-' 188.0 9-50 95.4 11-30 47.6 12.60 H 140 SEYLER AND LLOYD: The figures plotted on logarithmic paper lie very nearly on a straight line. McCoy gives values for k which are subject to correction for the diminished solubility of carbonic acid in saline solutions as shown by Stieglitz (Zoc.cit.): C. k uncorrected. Ic corrected. 100 x 10-3 5290 6397 3 00 4460 4691 1000 3120 3726 When k is plotted against logc (where c=coiicentration in milligram-equivalents per litre) the results lie nearly on a straight line k = 8739 - 1671 log c. We thus get values for I; correspond-ing with the concentrations in Shields's experiments : C. kd. k,. a calculated. 95.4 x 10-3 11-30 x 10-5 5400 0.775 188.0 9.50 4970 0.708 380.0 8.16 4450 0.680 The values for sodium acetate according t o Kohlrausch are: C. (36.4 x 10-8 188.0 380.0 a 0.785 0.739 0-660 The results are close enough t o show that no great error will be made by taking the dissociation of the sodium bicarbonate as equal to that of the acetate.The dissociation of sodium chloride is decidedly greater. The empirical formula for k,=S739 - 1671 log c serves t o express the results between c=lOOO and 100 but does not allow us t o calculate the value at infinite dilution. I f however by experi-ments a t t,he highest possible dilutions we can obtain an approxim-k a t b n to 2 = k a! a t such dilutions that a"= we should have k P data for calculating /3 a t least' approximately since I n the experiments to be described we determined k at dilu-tions c = 12.5 x 10-3 G = 10 x 10-3 and even c-5 x 10-3 and found that it approached a maximum value of 7124 which we take as '2. k3 This gives us the value of li,=4*27 x 10-11 and kcl = !?! = 19.2 x 10-5. k3 k p = -C a2. 7124 It also enables us to calculate fl from the formul STUDIES OF THE CARBONATES.PART 11. 141 Thus we get: C. kc. a. a2 B . 1*104-0*32010g C. ~ O O X ~ O - ~ 5397 0.783 0.613 0.464 0.464 300 4691 0.700 0.490 0.323 0.311 1000 3726 0,525 0.275 0.144 0.144 It will be found that' if fi is plotted against logc the result is a straight line P = 1.104 - 0.320 log c. This formula will enable us to evaluate fl approximately between c=100 x It probably holds good even a t far smaller concentrations since the formula 8739 - 1671 log c gives for c = 1 0 x 10-3 a value 7068 against 7124 found. Since a2=7124 Pit follows t h a t a is very well represented by and c = l O O O x 10-3. k, (1.104 - 0.32 logc) 8739 - 1671 logc ' t,he formula a2= 7124 The following values for a and P are calculated f o r round con-The concentrations are milligram-equivalents per litre : centrations.C X 103 50 100 200 300 400 500 700 800 1000 P 0-560 0.464 0.368 0.311 0.271 0.240 0.194 0.175 0.144 a 0.822 0.782 0.731 0.694 0.663 0.636 0.588 0.566 0.525 a2 -1 - ac. 190.4 x 10-3 281.6 398-6 472.4 523.0 556.8 588.9 592.4 579.4 NoTE.-These figures are carried out to three decimal places for purposes of calculation but it is not of course supposed that they are significant to anything like this degree. These values represent the activity of sodium carbonate t h a t is to say the active mass (as regards the CO ion) and of sodium bicarbonate (as regards the HCO ion) in equilibriuni with each other and with carbonic acid.Those for a are founded on the ionisation of sodium acetate calculated from the conductivity. The values for P are much smaller than would be expected from analogy to sodium sulphste even after allowing for the presence of ail intermediate ion NaSO (Harkins and Bray Zoc. cit.). There is however evidence shortly to be presented t h a t P really corresponds with the concentration of the CO ion and t h a t the dissociation is n o t represented by Na,CO = 2Na + CO, b u t by Na,CO = Na + NaCO and NaCO,= Na + CO,. I n the former case the sodium ion concentration would be 2[C03]=2fic where c is the molecular (not equivalent) concen-tration whilst the non-ionised sodium carbonate would be (1 - P ) c 142 SEYLER AND LLOYD: I n the latter case the sodium ion concentration will be greater, “a’] = 2[C03J + [NaCO,] whilst.the non-ionised carbonate will be smaller Cxa2coJ = c - [CO,] - [NaCO,]. If a be the degree of ionisation of sodium carbonate in the first stage we shall have CNa2Co3 = c(1- a) [CO,] = c p ; also since we have [NaCO,] = c - [CO,] - C N ~ ~ C O ~ = c - c/3 - C( 1 - a ) = c(a - /3). c = [CO,] +[ NaCO,] + Cha2c03, Further “a’] = 2pc + c(a - /3] = c(a + p). I n the mixtures such as we have been dealing with in which the bicarbonate largely preponderates we have assumed a to be the same as that of sodium acetate a t the same total sodium con-centration. I n this case the assumption will not be far from the truth. I n seeking t o apply the results to solutions of pure carbonate, Some other assumption with regard to the first-stage ionisation will have to be made since the sodium ion concentration of a solution of pure carbonate is undoubtedly less than that of a solu-tion of bicarbonate of the same equivalent concentration.It may be said that for the same reason the value of p will be different in a decinormal solution of pure carbonate from what it would be in a mixture consisting chiefly of bicarbonate. How-ever in McCoy’s experiments the carbonate varies from a trace to 32 per cent. whilst in those of Shields it varies from 100 per cent. to 50 and 20 per cent. without showing any noticeable drift in the constant. As a first assumption we shall assume that /3 is the same in all mixtures of carbonate and bicarbonate of the same total sodium concentration.Experiments on the value of L d = for piire carbonates would k a enable us to test the question. As regards a several assumptions niay be made. (1) That ~ r ~ ~ = k n is the same a3 for solutions of “a,C%I sodium acetate a t the same sodium ion concentration (Harkins and Bray loc. cit.). (2) That the degree of ionisation according to the first stage, Na,CO,=Na+NaCO, is the same as that of sodium acetate at the same total sodium concentration. (3) That i t is the same as that of sodium acetlate a t the same rnoIecular concentration. (4) That i t is the same as that of sodium acetate a t the same sodium ion concentration. Of these (1) and (4) require us to know approximately the total sodium ion concentration. This could be obtained roughly o STUDIES OF THE CARBONATES.PART 11. 143 assumption (2) or (3) and then corrected by a series of approxim-ations. Assumption (1) we think is very doubtful since I, varies with concentration and we do not know that its variation is dependent on the sodium ion concentration when [NaCO,] and [Na] are not present in equal quantity. I n the dissociation NaA = Na + A the negative and positive ions are equal in number but in the dissociation Na,C03=Na+ NaCO they are not since [NaCO,] is reduced and [Na] increased by the further reaction NaCO,=Na+ NaCO,. Assumption (3) has been used in the case of sodium bisulphate with success by Noyes (Cnrnegie Inst. Publication No. 63). We may use it as an approximation and calculate the value under assumption (4) therefrom (c = milligram-molecules per litre).- -Under assumption (3) we have the following results, 2c. 100 400 1000 2c. 100 400 1000 C. a. (l-a) B. 50 0.822 0.178 0.464 200 0.731 0.269 0.271 500 0.636 0.364 0.144 c. [Na,CO,]. [NaCO,]. [CO,]. [Na]. 50 8-88 17.9 23.2 64.3 200 53.70 92.0 54.3 200.6 500 181.80 246.1 72.0 390.1 (a-8). 0.358 0.460 0,492 E x 103. 129.7 343.6 528.1 (a+B). 1.286 1.002 0.780 ka x lo3. 83.3 118.3 114.1 If we use these figures for the sodium concentration to obtain t,he degree of dissociation a’ on assumption (4) and recalculate the sodium concentration therefrom we shall obtain the following values : 2c. 100 400 1000 2c. 100 400 1000 C. a’. (1 -a’). B. 50 0.80 0.20 0.464 200 0.69 0.31 0.271 500 0.58 0.42 0.144 c.[Na,CO,]. [NaCO,]. [CO,]. “a]. 50 10.0 16-8 23.2 63.2 200 62.0 83.8 54-3 192.2 500 210-0 218.0 72.0 362.0 (a’ - B ). 0.336 0.419 0.436 E x 103. 106.0 259.0 376.0 k is the value of the factor CNaI X [ NaCo21 bnd L Na,CO,I kb = “a1 x I C0,l . [ NaCO,] (a‘+B). 1.264 0.961 0.724 kb x lo3. 87.0 124.0 119.0 It is to be observed that kb (which is concerned only with ions) is not greatly affected by the assumption as regards a and is more nearly constant than k, which involves the concentration of the non-ionised salt. The value of k increases with the concentration but on eithe 144 SEYLER AND LLOYD: assumption is less than t h a t for sodium bicarbonate (or acetate) a t the same molecular concentration or sodium ion concentration.Th,e Vulzre of %.-This we calculated to be 19.2 x 10-5 at$ con-JG centrations of a b o i t 10 x 10-3 and under. I n order to check this we made some determinations of the value by Shields's method namely the velocity of hydrolysis of ethyl acetate. For c = 100 x 10-3 we obt'ained k d =12.69 x 10-5 11-72 12.15 mean 12.18 x 10-5. This result is rather higher than that calculat'ed from Shields's For c = 12.5 x 10-3 we obtained Ic,~ =21.5 x experiments namely 11.6 x 10-5. 22.2 21-8 A second series gave: 16.8 10-5 16.8 10-5 For some reason two experiments gave decidedly lower results The mean of all the experiments is 19.8 x The average would give lc,=4.15 x 10-l1. The Effect of Sodium Ghloride.-For the purposes of another investigation it was desired to know what effect would be pro-duced on the equilibrium of carbonat,es and carbonic acid by a salt with a common sodium ion such as sodium chloride.It was expected t h a t if in a decinormal solution of sodium carbonate the sodium concentration was raised to normal strength by sodium chloride the value of k would be diminished until it had about the same value as in a normal solution of pure carbonate and bicarbonate. It was found that k was indeed reduced but the value was about 23 per cent. higher than t h a t in the absence of sodium chloride. than the others b u t we could see no reason for rejecting them. Concentration of carbonate (equivalents). 100.0 x 10-3 100.0 1000*0 12.5 12-5 100.0 Concentration of sodium chloride.Total Na. k,. 0.0 100.0 x 10-3 5300 900.0 1000*0 3836 0.0 1000~0 3120 0.0 12.5 7124 87.5 100.0 6258 0.0 100.0 530 STUDIES OF THE CARBONATES. PART 11. 145 Hence starting with a pure N/lO-solution of carbonate for which kc=5300 the value of JsC decreases to 3120 when the sodium concentration is increased to N by carbonates of sodium but only to 3836 when the sodium concentration is due t o the chloride. That is to say the value of kc will depend not only on the sodium concentration but on the ratio of the chloride to the carbonate. k’ k C Let this ratio be called r then with r = 9 the value of - C = 1-23, k‘ For the dilute solutions of carbonate we have for 1-=7 L= 1.18. kc It thus appears that the effect of sodium chloride on k is of the same order for dilute or concentrated solutions and depends upon r the ratio of chloride t o base as carbonates.The effect of the salt must’ be due to the alteration of tho ionisation of the carbonate and bicarbonate since as before, It is to be expected that the ionisation of sodium bicarbonate will not be greatly affected by the presence of sodium chloride, but will have much the same value when the total sodium con-centration is the same whatever be the value of r. If this is the case the effect must be due t o the alteration of the ionisation of k’ p‘ kc P * the carbonate. Putting uf =a we have 2 = I n order to express the effect of salt we shall assume that fi’ has a similar form t o P that is can be expressed by the formula f i f = d - b f logc where c is the total sodium concentration in k’ a‘ - b’ log c k CL- blogc milligram-molecules.Then 2 = ~~~ . We have already found k,= 8739 - 1671 log c. For k’ we have a t c=100 kf,=5397. At c=lOOO we obtained 3836. This requires correction for the diminished solubility of carbonic acid which makes i t 4581. We then find kfc=7029-816 log c. k’ - 7029 - 816logc k, _ -8739 - 1671 logc ’ When c=100 we have no salt present and kfc=k,. If salt be added it is evident that c=100 ( r + l ) therefore log c =log (r + 1) + 2 whence k’ - 5397 - 816 log (r+ 1) 1 - 0.1512 log (Y+ 1) = _-- 5397 - 1671 log (r + 1) I - 0.3096 log (r +T) ‘ H 146 SEYLER AND LLOYD: Hence generally we have for P (assuming that the effect of ealt is the same a t other dilutions) 1 - 0.1512 log (r + 1) 1 - 0.3096 log (r + 1) ’ p = (1.104 - 0.320 1.g~) _ _ _ ~ - - - - - - -When no salt is present, r=O; this reduces to The effect of the salt was deduced from the experiments on N/lO-sodium carbonate but it must apply approximately to more dilute solutdons.For instance with N/80-solut~ions T = 7 T + 1 = 8, B= (1.104 - 0.320 log c). k’ we should get $ =1*22 against 1-18 found. E X P E R I M E N T A L . The object was t o determine the ratio of carbonate and bicarbonate in a very dilute solution in equilibrium with air containing a known amount of carbonic acid. Preliminary trials showed that a N/80-solution of sodium carbonate reached equil-ibrium with pure air when about 80 per cent.of the base existed as bicarbonate and 20 per cent. aa carbonate. Ordinary air there-fore contained a suitable percentage of carbonic acid. The actual amount of carbonic acid in the air used (drawn from outside the laboratory and washed) was determined by drawing the air in series through N / 10- and N/80-solutions of carbonate. I n order to be sure that equilibriunl was reached the check solutions of N/lO-strength were placed in some cases both before and after the dilute solution. The temperature was kept a t 2 5 O by a Hearson’s regulator and the solutions were agitated by being shaken in flasks (steamed Jens glass) on a small .truck running on rails at the same time that air from outside the laboratory was drawn through them. Special arrangements were made to prevent the liquids passing from one flask to the other.The amount of carbonic acid in the air was calculated ‘from the analysis of the decinormal solutions by McCoy’s formula, 2c xs 5300 1 -x * [H,CO,] = ___ -where c is the concentrat-ion of the base in equivalents 100x the percentage of bicarbonate in the liquid and [H2C03] the concen-tration of the carbonic acid. For the analysis of the liquid the method of double titration with phenolphthalein and methyl-orange was adopted with certain precautions. Kuster Lunge and Lohoffer and others have thrown grave doubts on the accuracy of this method alleging that it give STUDIES OF THE CARBONATES. PART 11. 147 results for the carbonate which may be 3 or 4 per cent. too high. Kuster attributes this to the supposed considerable alkalinity of bicarbonates t o phenolphthalein.McCoy has already shown that the alkalinity of bicarbonates is very small and Seyler (AnaZyst, 1897 22 314) showed that if loss of carbonic acid is avoided the results are correct to within less than 1 per cent. although usually on the high side. This question is the subject of an investigation by Xeyler and Tripp shortly t o be published. It was found that the point of neutrality to this indicator is very close to that required for the bicarbonate. It may be slightly on one side or the other. The end-point depends on the conditions of visibility of the colour the amount of indicator used and not only the total sodium concentration but the ratio of sodium chloride to bicarbonate a t the end of the titration.To avoid errors from this source the following precautions were adopted. Loss of carbonic acid was avoided by titrating in a tall Nessler glass adding the acid slowly from a burette with a long delivery tube reaching to the bottom of the vessel and stirring continually with a circular stirrer which was never lifted above the surface. Under these conditions it was proved that no appreciable loss of carbonic acid occurred even in fairly concentrated solutions. The amount of indicator was carefully measured and the colour a t the end-point compared with a check experiment. Other influences were allowed for as follows. A check experiment was conducted with each determination in which the conditions were the same as regards concentration of bicarbonate and sodium chloride.A standard solution (usually NjlO or N / 2 0 ) of sodium carbonate in boiled neutral distilled water was prepared and kept out of contact with carbonic acid. The standard hydrochloric acid was made with boiled water and acid and protected. An equivalent solution of neutral sodium chloride was prepared and protected. A preliminary titration was made with phenolphthalein and methyl-orange on the liquid t o be analysed. Let z be the number of C.C. of acid required with phenol-phthalein. Let m be the number of C.C. of acid required with methyl-orange. A comparison tube with the same amount of irdicator and an equal volume of water saturated with carbonic acid was used to judge the end-point. The standard employed was 2(m-z) C.C.of carbonate diluted to a given volume and very carefully titrated with phenol-phthalein. This was used as a comparison cylinder in the titra-H* 148 SEYLER AND LLOYD: tion of the liquid to be analysed. standard is: The final condition in the Sodium bicarbonate m - x C.C. Sodium chloride (m - x) C.C. (produced in the titration). If the titration differs from this by say y c.c. then y is the correction t o be applied to the titration. To the liquid to be analysed is added m - Zx C.C. of the salt solu-tion. A t the end of the titration the conditions will therefore be : The point of theoretical neutrality is m - x . m - 2 x C.C. bicarbonate pre-existing. x C.C. formed from carbonate in titration. Final bi-carbonate m - x. Sodium chloride ?rz - 2x added x formed by titration.Total a t end of titration m - x. of bicarbonate and chloride diluted to the same volume. was added to the standard to make the final amount the same. I n both etandard and assay there are thus the same amounts When the experiniental liquid contained sodium chloride this Example : Preliminary titratioii 10 C.C. required 711 = 20.21 C.C. N j20-acid. x= 5.94 Standard 2(m - x ) = 28.54 True bicarbonate m - x = 14.27 Required to phenolphthalein 14.11 y = 0.16 This has to be added t o the titration t o get the true result. Final titration m = 20.21 x= 5.83 m - 2x = 8.4 = salt added. Corrected figure for x 5.83 + 0.16 = 5.99. 10 C.C. contain 20'21 X ] Z O total base Carbonate 2 x 5.99 = 11.98 Bicarbonate = 8.23 Carbonate 40-7 per cent.Bicarbonate 59.3 per cent STUDIES OF THE CARBONATES. PART 11. 149 Example 2 : Prelimiiaury titratioit 50 C.C. required in = 12.58 C.C. N/20-acid. X = 1.23 Standard 22.7 C.C. = 2(m - X) 11.35 m - x Required t o indicator 11.14 Correction 0.21 to be added. F i n d titration ?n = 12.58 X = 1.14 True value of x = 1-14 + 0.21 = 1.35. Total base on 50 c.c.=12'58 N/20 Carbonate 2 x 1.35 = 2-70 Bicarbonate 9.88 Carbonate 21.5 per cent. Bicarbonate 78.5 per cent-. Besults of Experiments Temp. 25". Bicarbonate Carbonate C. 1002. 390 (1 -x). [R,CO,]. kc. 101-025 x lo- 42.18 57.82 0.01173 x 5300 12.55 80.51 19.49 0.01173 7130 12.627 80-63 19.37 0.01173 7228 100.8 40.47 59.53 0.01046 5300 100.5 40.60 59.40 0.01052 5300 12-58 78.53 21.47 0.01049 6892 101.05 40.72 59.28 0.0 1066 5300 100.50 40.89 59.11 0.01072 5300 12.45 79.60 20.40 0.01069 7233 We have then for c=12.5 x 10-3: k.,.7134 7228 6892 7233 mean 7124 -We put on record some experiments with N/150- and N/200-solutions although here the titration with phenolphthalein is so small that the correction becomes comparable in magnitude with it 150 SEYLER ANT) IALOYD: However they were very carefully made by the same method : C. 100x. 100 (1-x). [ H,COJ. k,. 6.540 87.48 12.50 0.01 100 7270 6.800 x 87.84 12.16 0.01 102 x 10-3 7830 4.870 4.872 4.410 5.300 89-80 10.20 0.01173 6468 90.22 9.78 0.01173 6920 90.24 9-76 0.01 100 6680 88-65 11-35 0-01100 6697 The average of these is 7123 identical with that for N/80-solu-Even a t N/200 the concentration of the hydroxyl ion is too tions.small to affect the results materially. This is still not large compared with 0.50 x 10-3 equivalents of base as carbonate or 4.5 x 10-3 equivalents of bicarbonate. Efiect of Sodiii tti Ghloride. Concentra- Con-tion centra-of base tion of Total as car- sodium sodium con-bonates. chloride. centration. io0.00 x 10-3 - 100-0 100.0 1 00*00 -100~00 900.0 1000*0 100~00 900.0 1000*0 12.58 - 12.580 12.04 87.5 99.54 12.00 87.5 99.50 1002. 40-83 40-61 36.40 36.10 78.53 77-24 77.83 100 (1 -5%) 59.17 59-39 63.60 63.90 21.47 22.76 22.17 [H,CO:,1. E,. 0.01035 -0.01220 -0.01035 3869 0.01022 3836 0-01490 6892 0.01035 6100 0.01022 6417 Hydrolysis of Sodium Cnrbor,nte b y Hydrolysis of Eth?/l rl c e t o t e .The symbols have the follow-ing meaning: Shields's method was followed. c =original concentration of the ethyl acetate in the mixture. c2= original concentration of the sodium carbonate in the x = number of gram-molecules of carbonate changed to bi-t=time in minutes. k = velocity-constant of hydrolysis of ethyl acetate. About 200 C.C. of the sodium carbonate solution (made with boiled distilled water) were mixed with 200 C.C. of a solutioii of neutral ethyl acetate of known strength. The initial time was taken as halfway between the beginning and end of the mixing mixture. carbonate STUDIES OF THE CARBONATES. PART 11. 151 of the solutions and the final time the beginning of the titration; 20 to 50 C.C.were withdrawn from tJme to time and titrated with N/20- or N/40-hydrochloric acid. The titration was made with the usual precautions to a very faint pink with phenolphthalein. The temperature was about 25O the solutions being maintained a t that temperature before mixing. The value of k was obtained by the formula (3'132 + k)(4472 - 2') = 192'07, which was found to represent the values given by Shields in the neighbourhood of 25O. Thus a t 25O we have k=6.608 (Gold-Schmidt Ber. 1899 32 3396 gives 6.94 a t 25O). The value of k d is found from the formula C C C C t . kkd = 2 log 2 - - loge - ' c - - 2 C 2 - X 1 c - c 2 c - X I We give the full experimental data in three typical casea. N/ IO-Sodiz~m Garbonate.Conditions similar to those of Shields. Temperature 25 1 O. 1. c2 - x. X. c - x . kk,r. 0 4 * 9 3 5 ~ 1 0 - ~ - 49.871 x -10 3-160 1.775 48.096 8.736 x lo-' 15 2.875 2.060 47.811 8.340 20 2.635 2-300 47.571 8.250 30 2.285 2-650 47.221 7.990 40 2.000 2.935 46.936 7.970 Average kkCl= 8.45 x lo-'. The following results were obtained : Temperature. c2. C. khi- E . k d * 25.1 4.975 37-765 8.09 6.658 12.15 25.1 4.950 23.400 '7.81 6.658 11-73 25.0 4.925 23.750 8.37 6.608 12-67 251O 4.935 x 10-2 49.871 x 8-45 x lo-' 6.658 12.69 x 10-6 N / 8O-Sodizlm Carbonate. I n these experiments a correction was applied t o the results to allow for the effect of the sodium acetate formed on titration. This was made by partly neutralising a similar solution t o that being titrated by acetic acid and comparing the hydrochloric acid required to comp1et.e the titration with the carbonate actually present.Thus in the absence of acetate the carbonate was correctly estimated a t 12-95 x 10-3. When the acetate was 8.38 x 10-3 and the carbonate 4.57 x 10-3, 4.67 C.C. of acid were required an excess of 0.1 C.C 152 SEYLER AND LLOYD: When the acetate was 11-52 and the carbonate 1.43 1.57 C.C. of hydrochloric acid were required an excess of 0.14 C.C. By graphic means the value of this correction was found for each titration and the corresponding deduction made. Temperature 25O 200 C.C. of A7/40-carbonate mixed with 200 C.C. of ethyl acetate solution (c =493-6 x 10-3). 50 C.C. withdrawn and titrated with N/40-acid. t .c2 - x. 2. c - x . kkd. - - 6.3600 x - 246.80 x 10-3 10.00 1.6860 4.674 242- 13 15-52 x lo-' 14.75 1.2820 5.078 241.73 14.15 20.00 0.8780 6.482 241.32 14.60 30.00 0.4739 5.886 240.92 14.62 Mean kkCl = 14.72 x ExDeriments conducted in this way gave: Temperature. c2. 25.00" 6.360 x 24-95 6.183 25.10 5.820 Two experinients gave for excluding them. 24.95" 6.010 24.95 6.075 C. EE'I. k. k,i. 246.80 x 14.72 x 10-4 6.608 22.2 x 253.20 14.52 6-633 22.9 182.65 14.24 6.658 21.4 lower results but we could see no reason 194-40 11.18 6.633 16.8 191.95 10.80 6.633 16.3 It is possible that these lower results are due to the highly dilute solutions having accidentally absorbed some carbonic acid. If B is the concentration of the bicarbonate originally present in the solution then the formula becomes k .k . t = B+c ~- log 2%- - 10ge c . c - c 2 c 2 - x c - c 2 c - x Nj200-temperature. c,. C. kkd. k. kd -25" 2.5 x 10-3 90.8 x 10-3 15.2 x 10-4 6.608 2 3 . 0 ~ CoizcZusions.-( 1) The apparent variations of the second ionisa-tion constant of carbonic acid in the equilibrium equation [HI x [CO,]=k,[HCO,] are due to the ionisation of the sodium bicarbonate (a) and t h a t of sodium carbonate ( P ) . The variation of the hydrolysis constant of sodium carbonate, k d = 2 k p - in Shields's experiments and of k,= k.1 - p - in McCoy's k3 a k3 a2 experiments is due to the same cause. has been estimated a t 4.27 x 10-11 and ',= 19.2 x 10-5 2= 71'34. (2) By experiments a t high dilutions the value of k a t 2 5 O k k3 1% (3) The value of a the ionisation of sodium bicarbonate either alone or in presence of sodium chloride or carbonate may be take STUDIES OF THE CARBONATES.PART 11. 153 as equal to t h a t of sodium acetate a t the same molecular con-centration. (4) The value of j3 the ionisation of sodium carbonate (in respect to the CO ion) between equivalent concentrations 1000 x 10-3 and 100 x 10-3 (and probably a t higher dilutions) may be approximately represented by the empirical formula p= 1.104 -0.320 log c where c is the sodium concentration in milligram-equivalents per litre. (5) I n the presence of sodium chloride the apparent value of /3 is greater than for pure bicarbonate and carbonate solutions a t the same sodium concentration. If 1’ is the ratio of sodium as chloride to sodium as bicarbonate and carbonate then 1 - 0.1512 log (?” + 1) p = (1.104 - 0.320 log c) .- ~ 1 - 0.3096 log (Y + 1) ’ These values are considerably less than those estimated on the usual assumptions from conductivity of the analogous salt, sodium sulphate but they represent the “active mass” of the sodium carbonate molecule a t the given concentration and probably the concentration of the CO ion. (6) It is confirmed that’ the ionisation of sodium carbonate takes place i n two stages namely Na,C03= Na + NaCO and NaCO = Na + CO,. The value of the second ionisation constant,” J i b = x[c031 I N ~ C 0 i calculated and shown to be smaller and more constant than is the first. ADDENDUM. Frary and Nietz ( J . Amer. Chem. SOC.1915 37 2271) have recently published a series of experiments on the hydrogen con-centration of solutions of pure sodium carbonate. By similar experiments on sodium hydroxide (the hydrogen concentration being measured by the electrometric method) they arrived a t a very improbable figure for E,, namely 1*76xlO-l4 a t 25O. Johnston (;bid. 1916 38 954) considers t h a t this result is explained by the neglect of contact potentials and that the most accurate figure obtainable is 0.8 x 10-14 (Lewis and Randall ibid., 1914 36 1979). This agrees with the value we have adopted. Frary and Nietz’s value seems impossible since i t would lead t o a figure for k =28 x 1 O - f ~ with the ordinarily accepted value for k3 but nearer 40x 10-5 with our value for k3. No investigator has found values approaching these figures.Prary and Nietz themselves even a t extreme dilutions (A’/ loo), It. 154 SEYLER AND LLOYD: find only 1 9 . 7 ~ 1 0 - 5 in agreement with our observations on the rate of hydrolysis of ethyl acetate. Nevertheless in considering t,heir further results one is justified in using their value of kw with their own experiments. Their experimental constant represents what we call Using the ionisation const,ants a’ for sodium hydroxide a for sodium bicarbonate and P f o r sodium carbonate (with respect t.0 the CO ion) we have ., = kd ’ k* a a . Taking t.he limiting value f o r this a t high dilutions to be 19.7 x 10-5 we can calculate by the formula p = kd a’a. k W l k 3 [It is not necessary that a a’ and fl should be the value unity At high dilutions at = a a t infinite dilution but only that /3 = aa’.nearly so that P=a2 is the condition that kd = ”-.I. k, Frary and Nietz give the following data from which we calcu-late B. We follow them in using for a and a’ the values for the estimated sodium ion concentration but the results would not be appreciably altered by taking the values for the total sodium concentration. B 8 (S. and L.) Equivalents Na con- concentra-4000 0.738 0,462 3.60 0.060 - -3000 0.728 0.453 3.62 0.060 - -2000 0.768 0-490 3.90 0.073 - -1416 0-784 0.636 4.45 0.095 - -1000 0.807 0.590 4.80 0.116 0,144 0.20 400 0.849 0.711 7.00 0.214 0.271 0.33 200 0.889 0-757 9.10 0.311 0.368 0-38 100 0.916 0.797 11.10 0.411 0.464 0.50 40 0.926 0.848 14.80 0-590 - -20 0.931 0.877 17-60 0.729 - -10 0.935 0.917 19.70 [0*867] - -Concentration of (S.and L.) a t same sodium carbonate. a t same Na ion per litre x lo3 a’. a. kLtx lo5. 8. centration. tion. It is worthy of note that the values used by Frary and Nietz for the total sodium ion concentration agree very well with those which we find. We have shown that [ N a ] = c ( a + p ) where c is the concentration of the sodium carbonate in milligram-molecules per litre. The degree of dissociation of the carbonate as regards sodium ions (that is the fraction of the total sodium existing as ions) i STUDIES OF THE CARBONATES. PART 11. 155 therefore = = p’. JVe compare a+P __ with p’ calculated 2c 2 2 by Frary and Nietz from the conductivity (a is here assumed t o be the same as for sodium acetate at the same molecular con-centration) : aCB.2c. a. B. 2 8’ 1000 0.636 0.144 0.39 0.39 400 0.731 0.271 0.50 0.47 200 0.782 0.368 0.57 0.54 100 0.822 0.463 0.64 0.60 This agreement must. mean t h a t the mobility of the NaCO ion is not f a r removed from t h a t of the CO ion but judging from the lower dilutions is probably somewhat smaller. The conductivity therefore is a fair measure of the sodium ion concentration assuming t h a t a t infinite dilution the ions are Na and CO,. The results of Frary and Nietz for j3 are of the same order as those obtained by us a t the same total sodium concentration, although a little lower and therefore do not’ vary in the direction required by comparison a t the same sodium ion concentration.Azcerbnch c u i d Pick’s Results ( A r b . Kais. Cesuizdkeitsnmt 1911, 38 243).-These authors have investigated the hydroxyl concen-tration of carbonates and bicarbonates and mixtures by colori-metric methods and arrived a t values for E agreeing with previous investigators namely about 6 x 10-1’. They realised the import-ance of the degree of ionisation but were hampered by the diffi-culty of forming an estimate of this factor. They also investi-gated the theory of the subject but as we think neglected to introduce the degree of ioiiisatioii a t the right stage. They coil-cluded that the hydroxyl concentration of a pure bicarbonate is independent of the concentration a result which is opposed to our experience. For mixtures of carbonate and bicarbonate they obtained for / 1 o-solutions [H~xCPP.= 7 . 3 x 1 0 - 11. CNn IT GO:: [ H] x CIVR~CO,~ p For these mixtures k,= - - ~ -Cr;a tr C O ~ 0. x -. Inserting our values B = 0.464 a= 0.783 we get k,=4*32 x 10-11, For 1C’/5-soIutions they obtained Putting P=0-38 a=0*71 we obtain X.,=4*33 x 10-11. These are the most favourable results for accuracy. Pure bicarbonate solutions are difficult to prepare and keep since slight in very good agreement’ with our estimate. cK@!3 = 8.1 x 10 -11. ( h a HC0 156 SEYLER AND LLOYD: alterations of the free carbonic acid make large differences in the hydroxyl concentration. The authors themselves lay little stress on their colorimetric measurements for pure carbonates. For bicarbonates however, they find a value 6.5 x 10-11 in A7/5- as well as in I\’/lO-solutions, and state that the hydroxyl concentration is independent of con-cent r a tio n .Hydrosyl Co?tcentrcitio?L of Mixtures of Ccwbonates and Bicarbonates. Auerbach and Pick on the assumption that the salts are fully ionised deduce the formula JCy=[H]- + [ H ] 2 e where a is the amount of sodium bicarbonate and b that of the carbonate (in milligram-molecules per litre) originally present without regard-ing ths hydrolysis. F o r pure bicarbonates b=O we get k,k2=H2 so that the hydroxyl concentration appears to be independent of the concen-tration. This would still be the case if we introduced the values a and p into the above formula. However this appears t o be erroneous. b a nk, The values of a and If a and b represent the amounts of bicarbonate and carbonate regarded as fully dissociated then the hydrolysis is represented by 2NaHC03= Na,CO + H2C03 and the bicarbonate really present is C Sa~co3 =a - 2[H,C0,1 and the carbonate must be introduced from the beginning.CNs,C03 = b + [H,CO,]. If the concentration is altered we shall have [HCO,] = ~ C ~ H C O ~ = a(a - 2[R2c03]), so that [H,CO 3 3 - - cL - CK:I13C03 of [H2C0,] will be different. as before though the actual value 2 A h [COJ == P C N ~ ~ C O ~ = P ( b + [H2C03]). Putting these values for LHCO,] and [CO,] into the equations F o r b=0 that is -for pure bicarbonate this reduces to k&3 = H2B STUDIES O F THE CARBONATES. PART 11. 157 Hence the hydroxyl concentration [OHl2=X/3 is not in-k,k, dependent of concentration but varies as the square root of P.This formula ceases t o hold good for very dilute solutions. The full expression may be deduced from the following equations : (1) a+ b =[HCO,] + [CO,] + (1 -a)(.-2[H2C03]) + (1 - P ) ( b + [H2C03]) + [H,CO,I whence aa + b p = [HCO,] + [CO,] + [H2C0,](Za - P ) . (2) [H]*[HCO,l =k,[H,CO,] and (3) [H]-[CO,] = k,[HCO,]. (4) 3[CO,] + [ KCO,] + [NaCOJ + [OH] = [Na] + [HI. (5) [Na] = a(a - 2[1I€,CO,]) + 2P(b + [H,CO,]) + [NaCO,]. Combining (4) and (5) we have (6) 2[CO,] + [HCO,] + [OH] =aa + 2bP+ 2[H&OJ(P -a) + [HI. Substituting the values of [HCO,] [H,CO,] and [cos] from equations (a) (3) and (4) in (6) and simplifying we have finally, (7) k&,= For infinite dilution a = P = l this reduces to Auerbach and Pick's equation.When u and b are not so small as t o be comparable with k2 arid k we may neglect k in the expression fla(n+2b)+li2 and (2a - P)k in k,bp - (2a - P)kw and E, in [H]aa - [HI2 + li, and the factor [H]k,k,. Also we may neglect [HI4 and its coefficients and [HI2 in com-parison with [Hlaa. The formula then reduces to that previously obtained: It holds rigorously for all dilutions. k - [H]2--&- ( a + "b) . p + [H] bP -. k2a aa 3 -When [HI is very small (as in mixtures containing a moderate amount' of carbonate) this becomes k,= [HI - b P . -. CLa When b = 0 (as in pure bicarbonate) it becomes k,k,= [HI". By combining (6) with (2) and (3) we get (na + 2bp + [ H])[H]' - kw[ [ I ] H,CO -- Bk,k + k 2 p ] - a(p-,)LHl3 158 STUDIES OF THE CARBONATES. PART IT. At infinite dilution this becomes aa+ZbP is not the total sodium ion concentration but that corresponding with the [HCO,] and [CO,]. I f we take the first-stage ionisation of the sodium carbonate to be the same as that of the bicarbonate a t the common sodium ion concentration then we have [NaCOJ = ( b + [H2C03])(a - P ) whence from equation (5) [Na]=au+ZbP+ ( u - P ) ( b -[H,CO,]). The sodium ion concentration is therefore greater than aa + 2bP (compare Johnston Zoc. cit.). Since the above was written Kendall ( J . Anzer. Chenz. SOC., 1916 38 1480) has determined k (the first ionisation constant of carbonic acid) a t different temperatures and finds a t Oo 2.24 x 10-7 a t 1 8 O 3-12 x 10-7 and a t 2 5 O 3.5 x 10-7. The value 3.5 x 10-7 should therefore be used in conjunction with the experi-ments carried out a t 25O. This does not alter the ratio '2 found by us a t 25O namely, 7120 nor does i t alter the calculation of the degree of ionisation of sodium carbonate. It does however alter the value of li (the second ionisation constant of carbonic acid) and gives a figure of 4.91 x10-11 instead of 4-27 x 10-11. It would also give k, k!.! =16.7 x 10-5 instead of 19.2 x 10-5 if the value of Ic is taken '3 a t 0.82 x -14 at^ 25O. Further careful experiments are required t o determine t,he variation of 5 with temperature which would enable us to ascertain how k varies with t,his factor. k3 TECHNICAL INSTITUTE, SWANSEA. [Rewioed October 27th 1916.

ISSN:0368-1645    

DOI:10.1039/CT9171100138

出版商:RSC    

年代:1917

数据来源: RSC

摘要:

RAY CADMIUM AND ZINC NITRITES. 169 XV1.-Cadmium and Zinc Nitrites. By PRAFULLA CHANDRA RAY. IN view of the contradictory statements of the previous workers in this field it seemed desirable to undertake a fresh investigation of cadmium and zinc nitrites. At the outset it may be pointed out that so far as the nitrite-forming capacity of mercury and cadmium is concerned the ques-tion is not one of the basic character of the metal. Mercury,* which occupies the lowest position in group I I B (in the electro-potential series) yields a fairly stable normal nitrite because both its chloride and nitrite are very feebly dissociated in aqueous solution (RBy and Dhar T. 1912 101 966). Thomsen found that mercuric oxide with its equivalent of aqueous hydrochloric acid evolves 18,920 calories whereas with its equivalent of nitric acid it evolves only 6400 calories and to this difference he ascribes the reason that an aqueous solution of mercuric nitrate is completely converted into chloride by the addition of an aqueous solution of hydrochloric acid.Mercuric chloride in aqueous solution is again completely converted into the cyanide by the addition of hydro-cyanic acid. Cadmium hydroxide also behaves differently towards the ordinary mineral acids. Thus whilst zinc and magnesium hydroxides with hydrochloric hydrobromic and hydriodic acids, respectively give almost the same value for the heat of neutralisa-tion namely about 19,500 calories with cadmium hydroxide the heat of neutralisation goes on increasing. Thomsen regarded the behaviour of cadmium oxide towards the above acids as exceptional, and on that account he refused t o class cadmium hydroxide in the magnesium group ( I ‘ Thermochemische Untersuchungen,” 111 279 e t Sep.; also English translation by Miss Burke p.129). The anomalous behaviour of cadmium is now easily accounted for. Its haloids are more feebly ionised than those of zinc and magnesium under similar conditions of dilution. I n fact it may be laid down as a safe guiding principle that a metal the haloid of which shows comparatively poor conductivity in aqueous solutions may be expected to yield a corresponding normal nitrite because as a rule its nitrite is also feebly ionised. The case of cadmium has been chosen as a crucial one. Conductivity measurement.s of cadmium chloride have been carried out by several investigators but as their results show con-* The author has pointed out that mercury occupies & twofold position in the Periodic System (see T.1905 87 180 ; also Chem. News 1914 109 85 160 RBY CADMIUM AND ZINC NITRITES. siderable discrepancy a fresh measurement has been made. It will be seen on reference to table I (p. 161) that at a dilution of 10 litres the equivalent conductivity of potassium chloride is 134 a t 29O that of cadmium chloride is 53 whilst t h a t of cadmium nitrite is only 33. Both these circumstances conduce to the stability of the nitrite and it has thus been isolated as a norinal salt. Zinc nitrite which can exist only in dilute solution under similar conditions has a conductivity of 73 (Riiy and Dhar T.1913, 103 13). It is well known t h a t zinc chloride is so readily hydro-lysed that on the addition of water a turbid liquid is obtained, due t o the formation of the compound Zn(0H)Cl. Zinc nitrite solution is acid and on concentration the nitrous acid set free decomposes according to the equation and thus zinc nitrate is continuously formed. The residue even if the evaporation is conducted in a vacuum is thus found to be a basic nitrate. E X P E R I M E N T A L . Cad?niuni N i t 1. it e . 3HN02=HN03 + 2NO + 2H20, Pure recrystallised cadmium chloride and silver nitrite were triturated in a mortar water being added from time to time until the filtrate gave no indication of excess of either of the parent substances; it was then evaporated in a vacuum over mlphuric acid.Bright pale yellow crystals were obtained which dissolved readily t o a clear solution. Preparation I11 was the product of double decomposition between calculated quantities of barium nitrite and cadmium sulphate : I. 0.3465 gave 0.2474 CdS. Cd=55.53. 0.035 , 4.35 C.C. N (nitritic) a t 29O and 760 mm. N = 13.79. 11. 0.2740 gave 0.1926 CdS. Cd =54*66. 0.1387 ,, 111. 0*0820 gave 0.0582 CdS. Cd(NO,) requires Cd = 54.90 ; N = 13.73 per cent. Apart from the results of the analysis the fact t h a t the salt did not lose its lustre even in an exhausted desiccator proves t h a t i t is anhydrous. Lang ( J . pr. Chenz. 1862 86 299) however, assigns to it the formula CC~(NO,)~,H,O. Several preparations were undertaken but in oiily two instances was the evaporated mass found to be partly insoluble in water (compare Vogel, 16.4 C.C.N (by combustion) a t 26O and 760 mm. N=13*26. Cd=55*20 RAY CADMIUM AND ZINC NITRITES. 161 Zeitsch. cinorg. C'hetn. 1903 35 402). Cadmium nitrite is ionised to a far greater extent than mercuric nitrite (Rky and Dhar T., 1912 101 966) and the tendency towards the formattion of a basic salt is thus easily explained. c'o n cln c 1 iv i f g Mecis I I re m en f s. The chloride was purified by recrystallisation (0.4391 gave CdCl,,H,O requires CdCl,= 91.50 per 0.6284 AgCl ; CdCl = 91.43. cent. ) . TABLE I. E p z~ ivn 7 PW t Co 11 rlzt r t i c i t y of Cd C1 ,H20 CL t 2 9 * 5 O. 21 ............... 10 20 40 so 160 320 640 X ............... 63-53 (33.60 73-76 84.4 94.31 102.1 104.15 Epttivnlenf C o 7 i d u c f ~ i ~ i t y of Cd(NO,) at 29O.21 ............... 10 20 40 SO 160 320 640 1024 X ............... 33.7 43.9 55.1 67.1 78.3 88.3 96.1 104.6 Decomposition b y Heat. The method of heating has been described in detail in the case of the alkali nitrites (loc. c i t . p. 180). The sa,lt began to deconi-pose slowly a t 1 5 0 O . The temperature was gradually raised t o 165O and finally to 230° when the ' click ' remained persistent. The gas which was collected in the reservoir of the mercury pump was found to be pure nitric oxide it being completely absorbed by an alkaline solution of sodium sulphite. The alkaline liquid in the glass spiral was washed out and was found to consist of a mixture of nitrite arid nitrate in the following proportion: Nitritic nitrogen = 3.Ni tFa t ic nitrogen ~~ The brown residue was found to be cadmium nitrate mixed with cadmium oxide. As nitric oxide was the chief gaseous product the main portion of the salt evidently decomposed according to the equation 3Cd(NO,) = 2Cd0 j- Cd(NO,) + 4N0. Side by side a parallel decomposition goes on thus: Cd(N0,)2 = CdO + N,O (NO + NO,). Divers has shown t h a t when nitrogen peroxide mixed with an excess of nitric oxide is passed into a solution of alkali pure nitrite is thereby produced (T. 1899 75 86). I n the present instance, although there was a large excess of nitric oxide the conditions of reaction were not comparable. The gaseous mixture was no 162 FRIEND NOTES ON THE EFFECT OF bubbled through a liquid but was quickly drawn across the glass beads moistened with alkali hydroxide.Moreover Dixon and Peterkin have shown that “the peroxide enters into’ a limited combination with nitric oxide” (ibid. p. 629). A small quantity of nitrogen peroxide is absorbed as such giving rise to the forma-tion of a nitrate as well. Z i m N i t r i t e . The salt was prepared by double decomposition between mole-cular proportions of zinc sulphate and barium nitrite. The filtrate, on evaporation in a vacuum left a white swollen mass which was practically insoluble in water. There was a thin membrane coat-ing the surface which on being broken up evolved nitrous fumes. During the concentration of the liquid nitric oxide was continu-ously evolved a portion of which remained imprisoned inside the thin superficial coating. The residue was boiled with a solution of pure sodium hydroxide and the alkaline liquid was found t o be free from nitrite and to contain only nitrate It will thus be seen that zinc nitrite solution on evaporation to dryness leaves a residue only of a basic nitrate. CHEMICAL LABORATORIES, PRESIDENCY COLLEGE AND COLLEGE OF SCIENCE, UNIVERSITY OF CALCUTTA [Received Februnrp lst 1917.

ISSN:0368-1645    

DOI:10.1039/CT9171100159

出版商:RSC    

年代:1917

数据来源: RSC

摘要:

162 FRIEND NOTES ON THE EFFECT OF XVK-Notes on the E’ect of Heat and Oxidation on Linseed Oil. By JOHN ALBERT NEWTON FRIEND. ALTHOUGH a considerable amount of work has been done on certain properties of linseed oil and the manner in which they are affected by heat and oxidation a few of the constants have not received the attention they deserve. Two years ago therefore the author decided to investigate the subject and although the work has had to be abandoned temporarily it was thought desirable t o place on record the results obtained. Two samples of oil were used namely best Baltic and best Cal-cutta raw linseed oil. They were obtained from a reputable firm, and having been purified by recognised commercial methods, further purification was deemed unnecessary HEAT AND OXIDATION ON LINSEED OIL.163 The Effect o f Hent on Linseed OiT. The molecular weight of linseed oil has occasionally been deter-mined by different investigators the figure obtained being of the order of 800. No systematic study of the subject however appears to have been made. Fahrion (Zeitsch. angew. Chem. 1892 5 171) noted that after being heated linseed oil lost much of its power of absorbing iodine and suggested that polymerisation had taken place. Fokin found that by heating the oil to 250-300° in an inert atmosphere a substance having a molecular weight approach-ing 2000 is obtained. Simiiar results have been achieved by Morrell ( J . SOC. Chem. Itid. 1915 34 105). E X P E R I M E N T A L . Samples of the same batch of pure Baltic oil were obtained, through the kindness of Dr.Morrell which had been "thickened" by heat but without appreciable oxidation as follows : Sample 1.-Raw oil. ,, ,, ,, 2.-Oil heated for thirty hours at about 200O. 3.-Oil heated for thirty-six hours a t about 300O. 4.-Oil heated for forty-two hours at about 300O. relative viscosit,ies and molecular weights were determined. The densities coefficients of expansion with rise of temperature, TABLE I. CoefIicient of Density Density expansion Relative Oil. at 0". at 50". 0-50". viscosities. 1 0.94444 0.90956 0.00076 100 2 0.94289 0.9091 2 0.00071 73 3 0.95804 0.9238 1 0.00074 459 4 0.9 7 2 6 7 0,93901 0*00072 3770 The coefficient of expansion steadily falls whilst the density and viscosity rise with the temperature and length of treatment.Sample 2 is interesting in that its density and viscosity are slightly lower than those for the raw oil. Possibly this is due to the pre-cipitation or flocculation " of certain constituents of the raw oil. The molecular weights were determined by the freezing-point met,hod in benzene solution.* * The author desires to thank Dr. W. E. S. Turner of Shcffield University, in whose laboratories the determinations were made for the necessary supply of benzene. Its melting point was 5.934" 164 FRIEND NOTES ON THE EFFECT OF Grams of oil in 100 grams Oil. of benzene. 1 17.53 10.22 9.89 2.69 Calculated a t infinite dilution . . . . . . 2 28.45 16.76 7.66 Calculated a t infinite dilution . . . . . . TABLE 11. Molecular weight, 624 673 704 733 744 594 667 738 760 Grams of oil in 100 grams Oil.of benzene. 3 31.74 21.07 18.84 10.33 Calculated at infinite dilution . . . . . . 4 22.42 14.58 7 . 6 2 Calculated a t in-finit,e dilution.. . Molecular weight. A75 778 794 897 lo00 995 1118 1270 1420 I n every case the apparent molecular weight increases with dilution. The results show that polymerisation takes place a t temperatures as low as 200° and increases in extent with the temperature and length of exposure t o the same. The Oxidation of Linseed Oil. When linseed oil is exposed t o the air it increases in weight, slowly a t first but rapidly later due t o the absorption of oxygen. A maximum point is ultimately reached after which a gradual loss in weight occurs.Many attempts have been made t o deter-mine the value for this maximum in the case of oils spread in thin layers on glass or other non-absorbent plates and the figures obtained have been used as bases of comparison of the relative I' drying" powers of the oils. I n 1913 Ingle (?7. Soc. Chem. Inc?., 1913 32 639) concluded that the maximum increase in weight is exactly double that' calculated from the iodine value thus suggest-ing the formation of peroxides during oxygen absorption. This afforded strong support to the belief that the iodine number is an approximate measure of the drying power of an oil as suggested by Hazura (Zcitsch. angew. CIicin. 1888 1 312). These experi-ments however ignore the fact that linseed oil during practically the whole period of its oxidation also loses appreciable quantities of water vapour carbon dioxide and organic vapours so that the total weight of oxygen absorbed exceeds the observed increase in weight of the oil by the weight of the vapours evolved.The latter amount is not negligible; in one experiment the total weight of oxygen absorbed was 2.5 times the observed increase in weight' of the oil a t the maximum point (Friend Proc. Paint Varnish Soc., May 14th 1914). The maximum point therefore does not represent the stage a HEAT AND OXIDA4TION ON LINSEED OIL. 165 which oxygen ceases t o be absorbed but a point of equilibrium a t which the oxygen absorbed exactly counterbalances the loss in weight due to escaping gases an6 vapours.Any factor that assists or retards the evolution of these vapours will proportionately lower or raise the maximum point. This serves to explain very largely the varied nature of the results obtained by different investigators, which results have ranged from 13 per cent. (Redman Weith and Brock J . Itid. Eiig. Cheni. 1913 5 630) t o 25.6 per cent. (Ingle, Zoc. c i t . ) the usual amount being approximately 18 per cent. in the case of raw oil spread in thin layers on glass plates to the extent of about 0.1 to 0.2 gram of oil per 100 sq. cm. (Lippert, Zeitsch. nrulew. Chetn. 1898 11 412; Weger ibid. 502). Whilst therefore the formation of peroxides may take place a11 accurate proportionality between the increase in weight and the iodine value must not be expected Ingle's results being largely a matter of accident.The foregoing methods of determining the drying powers of oils by noting the alteration in weight is thus merely of comparative value and only serviceable when carried out under precisely similar conditions for the diff erent oils concerned. It is essential t o emphasise these points in connexioii with the s u cc e ed ing results . Although the change in weight has been made the subject of repeated research no records appear to exist of any attempt to study the corresponcling changes in volume. That some change takes place is evident from the fad t h a t thick layers of oil in-variably crinkle on setting The results in table 111 were obtained as follows: Determinations 1-4 were made by passing air through a weighed quantity of pure Calcutta oil contained in a flask noting the alteration in weight and subsequently finding the density a t cliff erent temperatures, The fourth determination is slightly less accurate than the-previous three as the oil had thickened and frothed a small quantity rising in the form of bubbles up the flask and setting in the neck.The error was certainly small but appeared impossible to avoid. The device employed by Procter and Holmes ( J . SOC. C'hem. Znd. 1905 24 1287) could not be adopted as the oil was relatively near its setting point and any drops rapidly solidified when separated from the bulk of the liquid. I n a somewhat similar experiment Mulder (" Die Chemie der austrocknenden Oele," Berlin 1867 p. 114) found t h a t his oil became solid after increasing in weight by 10.5 per cent.This however can only be an approximate figure owing to frothing so no attempt was made to coiifirm it the remaining data in table I11 being- obtaine 166 NOTES ON THE EFFECT OF HEAT AND OXIDATION ETC. iii another way. The oil was spread on glass plates in thin layers containing about 0.1 to 0.2 gram per 100 sq. cm. This thickness gives trustworthy results (Lippert loc. cit. ; Weger Zoc. c i t . ) and has the advantage that i f through unequal distribution the oil is even considerably thinner a t any place no appreciable error is entailed (Wise and Duncan J . Znd. Bng. Chem. 1915 7 202). The alterations in weight were noted and the densities deter-mined by removing portions of the film with a knife under air-free water to which sodium chloride solution was subsequently added until the liquid possessed the same density as the solid.The fifth determination was difficult to obtain as the tacky film adhered to the knife. Eventually however the film was scraped off with crystals of zinc sulphate and as these dissolved in the water the oil was left without attachment and sank or floated according to circumstances. It is unfortunate that tha fourth and fifth results should be slightly less accurate than the others since it is impossible to decide from them whether any contraction or expansion takes place at the time of setting. TABLE 111. Experi-ment. 1 2 3 4 5 6 7 8 9 Percen-tage increase Condition in Density of oil.weight. a t 0". Raw oil ... ... - 0.94208 Liquid ... ... 2.08 0.95906 Do. ... ... 5.83 0.98736 Thick frothy liquid ... 9.66 1.01161 Tacky ... ... ... 14.14 -Just set ... ... 17.34 -Solid linoxyn ... 17.90 -Do. at point of maxi-mum weight ... 18-57 -Do. three months old 10.3 -Coeffic-cient of expan -Density sion a t 15". 0-15". 0,93179 0.00074 0.94850 0.00074 0,97696 0.00071 1.00123 0*00069 1.0424 -1.0582 -1.0656 -1.0902 -1.1054 -Perccn-tage increaso in volume a t 15". -0.28 0.87 2.06 2.0 3.3 3.1 1.4 -7 Under the particular conditions of the experiments therefore, the raw oil on setting a t 1 5 O expanded by 3.3 per cent. and then slowly contracted. The maximum increase in weight was 18'57 per cent.but the increase in volume reached its maximum befqre this namely at the setting point. The density of the oil Bteadily increased whilst the coefficient of expansion fell. Sabin ( J . Incl. Eng. Chem. 1911 3 84) mentions that a film of raw oil exposed to the air for eight months yielded linoxyn of density 1.098 the total gain in weight of the oil being about 2 per cent. No statement is made of the density of the original oil but assuming it to have the value of 0.932 the shrinkage must hav RELATION BETWEEN CHEMICAL CONSTITdTION ETC. 167 been 13.4 per cent. This lends support t o determination 9 in table 111. It is important to observe that the expansion is a function of the increase in weight. Any factor assisting the decomposition of the oil lowers the maximum point and reduces the expansion. Sabin (loc. cit.) and Gardner ( J . Ind. Eng. CJbenz. 1914 6 91) found that linseed oil when mixed with even chemically inert powders such as barytes and silica exhibits a smaller increase in weight 011 setting the powder apparently catalytically assisting the decomposition of the peroxide compounds. It would thus appear difficult to calculate the amount of expansion t o be ex-pected in any particular case. Tauber (Chern. Zeit. 1909 33 85 94) suggests that the crack-ing of paint surfaces is due to tension caused by electrical action of the pigments suspended in the linoxyn. In view of the fore-going results it is evident that the contraction suffered by the linoxyn on prolonged exposure to air is quite sufficient explanation for the cracking of old paint,. THE VICTORIA INSTITUTE, WORCESTER. [Received February 15171 1917

ISSN:0368-1645    

DOI:10.1039/CT9171100162

出版商:RSC    

年代:1917

数据来源: RSC

摘要:

RELATION BETWEEN CHEMICAL CONSTITUTION ETC. 167 XVIII .-Relation between Chemical Constitution and Physiological Action in Certain Substituted Aminoalkyl Esters. Part 11. By FRANK LEE PYMAN. SOME years ago (T.) 1908 93 1793) the author described the pre-paration and physiological properties of a number of aininoalkyl esters and subsequently with Jowett (Proc. Seuenth Iiiterilat. C'o~y. A4ppl. Chern. 1909) discussed the relation between chemical consti-tution and physiological action in these and other similar com-pounds. A number of substances which were prepared about that, time have not yet been described and the present paper is written with the object of putting their chemical and physiological proper-ties on record. The physiological tests ware carried out during 1908-1910 a t the Wellcome Physiological Research Laboratories by Dr.H. H. Dale F.R.S. and Mr. C. T. Symons to whom the author desires t o tender his best thanks. It had previously been shown that replacement of the benzoyI by the phenylacetyl group leads in the case of cocaine to a substanc 168 PYMAN RELATION BETWEEN CHEMICAL CONSTITUTION devoid of local anzesthetic properties (compare S. Friinkel “ Die Arzneimittel-Synthese,” 1912 p. 349) but in tlie case of a-eucaine to a substance having local anzesthetic properties (Vinci Vircli. Arch. 1898 154 549). With the object of testing the effect of a similar substitution in the local anzesthetics ethyl paminobenzoate (‘ anzesthesine ’) and P-diethylaminoethyl paminobenzoate (‘ novo-caine ’) the two substances ethyl paminophenylacetate and P-di-ethylaminoethyl p-arnitiopl~eiiyl~tcrtccte were prepared.The first was tested in the farm of a 5 per cent. solution in olive oil and the second in the form of a 5 per cent. aqueous solution of the hydr-iodide ; neither showed any local anmthetic propesty. It had been found (T. 1908 93 1794) that the salts of aminoalkyl esters of the general forinula R*CH,*CH( O*COPh)*CH,*O COPh (R = NMe, NEt, NC,H,,) were possessed of very considerable local anaesthetic action but were distinctly toxic and irritant and also acid in reaction. A substance of a modified type was now pre-pared in which one of the berizoyl groups was replaced by a phenyl group. First ~-dietILyltcrni~~o-Pf-i~herio,r~~isoyl.opyl cilcohol was ob-tained by the interaction of plieiiyl glycido ether and diethylamine, Another line of work was suggested by earlier results.PhO*CHI,*CH-CH + NHEt = PhO*CH,* CH(OH)*CH,.NEt,, \/ 0 a nietliod which had previously beeii euiployed fos the preparation of fi-arnino-/Y-o-tolyloxyisopropyl alcohol from ammonia and o-tolyl glycide ether by Boyd and Knowltoii (T. 1909 95 1803; compare also Boyd T. 1910 97 1791) and from this tlie beti;oyl derivative was prepared but aqueous solutioiis of its salts were so strongly acid t h a t they could not be tested satisfactorily for local anzesthetic properties. The hydrochloside of the amino-alcohol itself however, produced a distinct degree of local anaesthesia when tested in 5 per cent. aqueous solution. Fourneau (b. Plictrtrz. C’Iiinz.[vii] 1910 1, 55 97) has also prepared a number of amino-alcohols of this type, and sta,tes t h a t they have remarkable antipiretic and analgesic properties. A n aminoalkyl ester of a different type 8-beiizuyloxy-l-nicthyl-1 2 ; 3 :$-tetmli~/nrotyztitiu7;t~(? was prepared by benzoylating the parent compound; it gave a hydrocliloride so strongly acid t h a t it could not be tested physiologically. An attempt was then made t o prepare the corresponding paminobenzoyl derivative. F o r this purpose 8-p-~iitrobe~~zoylo~x:?/-~l-rrictl~l-l 2 ; 3 4-teti.ccliydl.ozuinolilze was first made but suffered hydrolysis so readily that the work was disc on tinued . I n connexion with this investigation it appeared t o be of interes AND PHYSIOLOGICAI; ACTION ETC. PART 11.169 to test p-Q.minobenzoy~pphenetidine a substituted amide of paminobenzoic acid. This substance is almost insoluble in water, and when introduced in powder into the conjunctival sac caused no local anmthesia, EXPERIMENTAL. E thy1 p-A minopheaylncetn t e. This ester had been prepared previously by Salkowski (Ber. 1895, 28 1917) by the action of boiling alcohol on the hydrochloride of paminophenylacetic acid ; he gives the melting point as 49.5O. The material required for the present investigation was obtained by the reduction of ethyl p-nitrophenylacetate by means of iron filings and dilute acetic acid. When dissolved in hot water and cooled with ice i t separated in nearly colourless glistening microscopic plates which melted a t 51° (corr.). (Found C=67.1; H = 7 * 2 ; N=7.9.Calc. C=67*0; H = 7 * 3 ; N=7*8 per cent.) P-Diet7~ylnmiizoethyl p-ivitrophe?zylacetate, N0,-C,H,*CH2*C0,*CH,*CH,-NEt2. The p-nitrophenylacetyl chloride required for the preparation of this ester was made by the action of phosphorus pentachloride on p-nitrophenylacetic acid. Its preparation has since been described by Wedekind (dniinZen 1911 378 288) who gives the melting point as 47O. The material used in the present investigation crystal-lised from light petroleum in very pale yellow thin serrated plates which melted a t 48O (corr.). (Found C=47.8; H=3*2. Calc., C = 48.1 ; H = 3.0.) Ten gram; of B-diethylaminoethyl alcohol were converted into the hydrochloride dried powdered and mixed with 20 grams of p-nitrophenylacetyl chloride.The mixture was heated for one hour in the water-bath dissolved in water and extracted with ether t o remove non-basic matter. The aqueous solution was basified with sodium carbonate and extracted with ether which removed 13.8 grams or brown oil. This was mixed with absolute.alcoholic hydrogen chloride when 10.9 grams of B-diethylaminoethyl p-nitro-phenylacetate hydrochloride melting a t lOSo separated. The hydrochZoride crystallises from absolute alcohol in prisms which melt a t 1 1 1 O (corr.) and are anhydrous. Found C = 53.5 ; H = 6.8 ; C1= 11.3. C,,H,,O,N,,HCl (316.7) requires C = 53-1 ; H = 6.7 ; Cl=11*2 per cent. The hydrobromide crystallises from ethyl acetate in very pale yellow prismatic needles which melt at 122-124O (corr.) and are VOL.CXI. 170 PYMAN RELATION BETWZEN CHEMICAL CONSTITUTION anhydrous. ingly so in alcohol or ethyl acetate. It is somewhat sparingly soluble in water and spar-Found C= 46.9 ; H = 5.9 ; Br = 22.2. C,,H,,O,K;,,HBr (361.2) requires C = 46.5 ; H = 5.9 ; Br = 22-1 per cent. P-Dieth ylu min oet hyl p-A minophe?hylacetat e , NH,*C,H,*CH,*C02*CH,*CH2*NEt,. Twenty grams of /3-diethylaminoethyl pnitrophenylacetate hydro-chloride 200 C.C. of water 5 C.C. of glacial acetic acid and 20 grams of iron filings were mixed ar,d warmed on the water-bath for two hours with frequent shaking. After filtering making aIkaline with sodium carbonate and extracting with chloroform 2'4 grams of a brown oil were obtained which gave 2.2 grams of the crystalline hydriodide. The hydriodide crystallises from absolute alcohol in f ern-like plates which melt a t 155-157O (corr.) and are anhydrous.It is soluble1 in water to the1 extent of about 4 per cent. at 25O and 10 per cent. a t 35O giving a neutral solution; it is sparingly soluble in alcohol. C,,H2,0,N,,HC1,(378.2) requires C = 44.5 ; H = 6.1 ; I = 33.6 per cent. The poor yield was due to hydrolysis of the ester. Found C = 44.9 ; H = 6.0 ; I = 33.4. P-Dietkylanzino-St-l~he12oxyisoy~~opyl A Icokol, PhO * CH,*CH (OH) =CH,.NEt,. Fifteen grams of phenyl glycide ether and 8.0 grams of diethyl-amine were heated in a sealed tube for five hours a t l l O o . The resulting oil was dissolved in ether washed with water and ex-tracted with dilute hydlrochloric acid. The acid extract was basified with sodium hydroxide and extracted with ether.The ether residue amounted to 21.5 grams of oil which distilled completely a t 178-179O under a pressure no6 accurately recorded but probably in the neighbourhood of 30 mm. The distilled base was converted into the hydrochloride which is very readily soluble in water or alcohol but can be crystallised from ethyl acetate. It melts a t 90-92O. C,,H,,O,N,HCl (259.7) requires C = 60.1 ; H = 8.5 ; C1= 13.7 per cent. Found C=60*2; H = 8 * 7 ; C1=13*8. &Diet hylamirzo-P'-phenoxyisolvroinyl Bemoa t e , PhO*CH,-CH( O*CO-Ph)*CH,*NEt,. Ten grams of /3-diethylainino-~'-plieiioxyisopropyl alcohol regen-erated from the pure liydrocliloride were beiizoyIated by th AND PHYSIOLOGICAL ACTION ETU. PART II. 171 Scliotteii-Baumann method yielding about 13 grams of crude base.This was converted into the riitrccte which is very sparingly soluble in water and was purified by recrystallisation from ethyl acetate. The pure salt melted a t 100-103°. Found C = 61.4 ; H = 6.8. C,H,,O,N,HNO (390.3) requires C= 61.5 ; H = 6.7 per cent. The base regenerated from the pure nitrate did not crystallise but a number of crystalline salts were prepared from it. The hydrocldom'de which is easily soluble in water giving a n acid solution melts a t 107-109°. Found C = 66.1 ; H = 7.3 ; C1= 9.9. C,,H,,O,N,HCl (363.8) requires C = 66.0 ; H = 7.2 ; Cl= 9-7 per cent. The hydrobromide melts a t 114-115O after crystallisation from benzene and dissolves in about. 70 parts of cold water. Foulzd C = 58.4 ; H = 6.5.C,,H,,O,N,HBr (408.2) requires C = 58.8 ; H = 6.4 per cent. The hydrz*odide melts a t 112-113O after crystallisation from The Izydrogen oxnlate melts a t 112-114O after crystallisation Found C = 63.3 ; H = 6.6. C,oH,50,N,C,H,0 (41 7.3) requires C = 63.3 ; H = 6.5 per cent. benzene; it is almost insoluble in water. from ethyl acetate. 8-13enzo?/lo~y-l-?nethyl-l 2 3 4-tetrahyclropziir~oline. Ten grams of 8-hydroxy-1-methyl-1 2 3 4-tetrahydroquinoline were benzoylated by the Schotten-Baumann method and t h e pro-duct was extracted with ether. It was removed from the ether by dilute hydrochloric acid regenerated by sodium carbonate and again extracted with ether. The ethereal residue amounting to 12 grams was converted into the hydrochloride which was crystal-lised from absolute alcohol yielding 8.7.grams melting a t 1 8 8 O .The base crystallised when liberated from the pure hydrochloride and melted a t 58-59O after crystallisation from light petroleum. Found C = 76.7 ; H = 6.4. The hydrochloride prepared flrom the pure base still melted at C,,H,,O,N (267.2) requires C = 76.4 ; H = 6.4 per cent. 1 8 8 O . Its aqueous solution was strongly acid. 8-p-Nitrob enzoyloxy-1-methyl-1 2 3 4-tetra~~dropzcinolilze. Ten grams of 8-hydroxy-1-methyl-1 2 3 4-tetrahydroquinoline were1 dissolved in 160 C.C. of 10 per cent. aqueous sodium hydroxide and well shaken with 30 grams of pnitrobenzoyl chloride dissolved I 172 MYERS BORIC ANHYDRIDE AND ITS HYDRATES. in chloroform the mixture being kept cold.A quantity of sodium pnitrobenzoate separated and was rem,oved by filtration. The chloroform Iayer of the filtrate was dried distilled to remove the solvent and the residue was crystallised from acetone when 3.0 grams of the above compound were isolated in a pure state, melting a t 127-128O. Found C=65.8; H=5*2. C,,H,,04Nz (312.2) requires C = 65.4 ; H = 5.2 per cent. This compound readily undergoes hydrolysis when boiled with alcohol with the formation of 8-hydroxy-1-methyl-1 2 3 4-tetra-hydroquinoline p-nitrobenzoic acid and ethyl pnitrobenzoate. p-NitrobenaoyZ-p-;xrhenet~ine NO,*C,H,*CO*NH*C,H,*OEt. Twenty-five grams of pnitrobenzoyl chloride were melted and poured on 18 grams of freshly distilled p-phenetidine. A vigorous reaction took place hydrogen chloride being evolved and a yellow Bolid melting a t 170-185O resulte'd. After crystallisation from dilute alcohol it formed matt'ed yellow needles which melted a t 186-1 87'. p-4 mino b eiaaoyZ-p-phe~zetidi.lze NH,. C,H,* CO *NH*C,H,*OEt. This substance was prepared by the reduction of p-nitrobenzoyl-pphenetidine with iron and hydrochloric acid in alcoholic solution. It crystallises from alcohol in colourless needles which melt a t 157-158O. It is almost insoluble in boiling water sparingly so in cold alcohol but readily so in hot alcohol. Found C = 70.5 ; H = 6.3. THE WELLCONE CHEMICAL WORKS, C,,H,,O,N (256.2) requires C = 70.3 ; H = 6.3 per cent. DARTFORD KENT. [Received February 27th 1917.

ISSN:0368-1645    

DOI:10.1039/CT9171100167

出版商:RSC    

年代:1917

数据来源: RSC

摘要:

172 MYERS BORIC ANHYDRIDE AND ITS HYDRATES. XIX.-Bo& Anhydride and its Hydrates. By JAMES ECKERSLEY MYERS. THE researches of Ebelmen and Bouquet (Ann. Chim. Phbys. 1846, [iii] 17 63) and Holt (Mem. Manchester Phil. SOC. 1911 55, No. lo) on the relations between boron trionide metaboric and orthoboric acids have led to the conclusion that metaboric acid is a definite substance but there remain a number of outstandin MYERS BORIC ANHYDRIDE AND ITS HYDRATES. 173 points which require elucidation before our knowledge of these substances can be regarded as satisfactory. Holt was able to show that in aqueous solutions of varying concentration orthoboric acid exists in the form of simple mole-cules but owing no doubt, to the ease with which boron trioxide and metaboric acid react with water information is lacking with regard t o the molecular condition of boron trioxide and metaboric acid and to the rate of reaction between these two substances and water.The present communication describes attempts made t o provide further information on these points relating to the nature and reactions of the boric acids which have not been fully dealt with by previous workers. The Rate of Reaction between Baroi~ Trioxide and Water. It has always been assumed that boron trioxide and metaboric acid react with water at such a high speed that it would be impossible t o measure the rate of reaction or the molecular weight of either in aqueous solution. Both substances dissolve in other solvents such as alcohol and acetone but these solvents are un-suitable for cryoscopic measurements and the volatility of the solute in the boiling solvents render ebullioscopic measurements useless (Firth and Myers T.1914 105 2887). When boron trioxide is placed in water even if it be in a finely ground condition such as is obtained by grinding the particles of the glass in an agate mortar the anhydride does not dissolve immediately. This phenomenon which is also observed in the case or" other glasses such as fused metaphosphoric acid is apparently due to the physical condition of the solid. After the boron tri-oxide has been in contact with the water for a minute or two a reaction takes place quite suddenly which is marked by a notable change in the volume of the solid. The solid which is produced dissolves fairly rapidly in water.The phenomenon which indi-cates some hydration of the boron trioxide may be easily repeated a t a very much slower rate by exposing the substance to a moist atmosphere when there is a gradual and easily detected change from the hard glassy material to a light powdery substance of much greater volume than that of the original anhydride. Use has been made of this behaviour to measure the rate of hydration of boron trioxide. Further qualitative information on this ma.tter was obtained by the following experiments. Boron trioxide metaboric and orthoboric acids were dissolve 174 MYERS BORIC! ANHYDRIDE AND ITS HYDRATES. in water and to the solutions were added portions of potassium iodide-iodate solution for the purpose of detecting hydrogen ions.Orthoboric acid is of course very little ionised in solution but after a minute or two a liberation of iodine was apparent although a considerable time elapsed before the maximum amount of colour developed. I n the case of the other two solutes there was no immediate coloration and in some cases two or three hours were required to produce a colour comparable with that obtained with orthoboric acid. The length of time required for iodine to appear was apparently proportional to the concentration of the solute and generally was about the same for boron trioxide and metaboric acid. It may be mentioned that metaboric acid exhibits some differences in its behaviour towards potassium iodide-iodate solu-tion in that some specimens react quicker than others and i t may be suggested that this is due to a difference in the mclecular com-plexity in the metaboric acid due to its method of preparation.Holt is of the opinion that metaboric acid may exist in two forms, one vitreous and the other crystalline; according to the tempera-ture used for its preparation. It appears also that the rate of formation of metaboric acid from orthoboric influences the mole-cular condition of the product. The behaviour of boron trioxide metaboric and orthoboric acids towards potassium iodide-iodate solution indicates it is submitted, that although boron trioxide may become hydrated to metaboric acid very rapidly a much longer time is necessary for the next stage of the hydration. It may therefore be possible t o calculate the molecular weight of metaboric acid in a freshly prepared solu-tion sufficiently accurately a t any rate to decide the molecular complexity of the substance in solution and also to derive some information respecting the order of the reaction between metaboric acid and water since if the freezing point of the solution remains constant the reaction taking place in the solution is one of the first order.The hydration of metaboric acid is hastened by the addition of mannitol as one would expect with an acid so little ionised. The rate of hydration of boron trioxide was measured by ex-posing a weighed quantity of the substance to an atmosphere saturated with water vapour a t a constant temperature. The solid was placed in a shallow weighing bottle which was placed in a larger vessel containing water and the whole maintained a t a constant temperature.Two methods were employed for obtaining a suitable surface of the boron trioxide. The first was to make a thin regular layer of the finely ground material in the ordinary way and the secon MYERS BORIC ANHYDRIDE AWD ITS HYDRATES. 175 was to dissolve the boron trioxide (or metaboric acid) in dry alcohol pour the solution into the shallow vessel and then evaporate the alcohol carefully and allow the vessel t o remain in a vacuum desiccator containing calcium chloride until quite free from alcohol. It was found that a very thin even layer could be obtained by the latter method if the vessel used was cleaned care-fully before introducing the alcoholic solution. The weighing bottle was removed from the moist atmosphere from time to time closed and weighed.The values for a typical example of this hydration are given in table I. TABLE I. Boron trioxide. Time in Grains. minutes. 1.2945 120 250 1350 1800 3060 4500 8640 Weight of product. Grams. 1.334 1.377 1.650 1.713 1.865 1.951 2.011 Gain. Gram. 0.0405 0.083 0.356 0.41 8 0.570 0-656 0.717 It will be evident from the values given above that the hydra-tion of boron trioxide proceeds farther than the stage of meta-boric acid under the conditions employed. It will also be seen that comparatively early in the reaction (after about twenty hours) sufficient water has been taken up to transform the whole of the boron trioxide into metaboric acid but that the further hydra-tion to orthoboric acid requires a very much longer period.These facts bear out the conclusions derived from the qualitative experi-ments with potassium iodide-iodate solution. Owing to the fact that it has not been found possible to devise any means of analysing the product of hydration it is not possible to express the values given in table I in the form of an order of reaction. It appears probable however that metaboric acid is one stage of the reaction but a t the same time it seems likely that a factor that will influence the rate o€ reaction is the degra-dation of molecular complexes of which boron trioxide glass is probably composed. Such a degradation is known to take place in the case of other glasses such as metaphosphoric acid (Holt and Myers T.1911 99 384). The values given in table I have been plotted as a graph (Fig. l), the time being taken against the increase in weight and it is shown very clearly that the first part of the reaction is relatively much faster than the latter part. Since i t has been established that metaboric acid is probabl 176 MYERS BORTC! ANHYDRIDE AND ITS HYDRATES. one stage in the hydration of boron trioxide the next measure-ments made were those of the hydration of metaboric to ortho-boric acid. The experiments were carried out in a way similar to that already described for boron trioxide and the results obtained are given in table 11. Gain in weight in grams. X I I I I I I I I I , 0 I / +=------I The values for k are calculated on the formula for a unimole-cular reaction assuming that the metaboric acid is hydrating to orthoboric acid.These values show a certain regularity which probably indicates that this reaction is a unimolecular one. The general rising tendency of the values for b suggests however that the molecular condition of the metaboric acid affect's the rate of the reactioq MYERS BORIC ANHYDRIDE AND ITS HYDRATES. 177 Metaboric acid. Time in Grams. minutes. 1.451 30 65 105 225 255 403 560 715 765 1195 TABLE 11. Weight of product. Grams. 1-478 1.509 1.545 1.644 1.666 1.741 1.817 1.884 1.908 1.981 Gain. Gram. 0.027 0.058 0.094 0.193 0.215 0-290 0.366 0.433 0.457 0.530 k. 0.00067 0.00069 0.0007 0.00076 0.000 7 6 0.00072 0.00074 0.000 7 9 0.00084 0- 00080 Further information on this question of the mode of hydration of metaboric acid was obtained by a number of freezing-point determinations.From the evidence derived from the behaviour of solutions of inetaboric acid and from the rate of hydration of the acid in an atmosphere of aqueous vapour it is concluded that this reaction is a comparatively slow one and if boron trioxide is dissolved in water the metaboric acid which is immediately formed does not at once change to orthoboric acid. If this conclusion is correct measurements of the depression of the freezing point of a solution made by adding a known quantity of boron trioxide to water should indicate in the first place the molecular condition of metaboric acid in solution and secondly, the order of reaction of the hydration.A solution was prepared by dissolving 0-218 gram of boron tri-oxide in water and as soon as solution was complete the freezing point was determined. This was found to be 2-49O on an arbitrary Beckmann scale. After a day had passed when the solution would undoubtedly consist of orthoboric acid the freezing point was measured again and was found t o be unchanged. This freezing point indicates a depression of 0.47O. Since 0.218 gram of boron trioxide would give on hydration 0.274 gram of metaboric acid the freezing point determined indicates that in aqueous solution metaboric acid exists in simple molecules. Further since the freezing point remains constant during the hydration to orthoboric acid the reaction may be stated to be one of the first order.If 0.387 gram of orthoboric acid is produced from the quantity of boron trioxide used Holt's conclusion that orthoboric acid exists in simple molecules in aqueous solution is confirmed. It was not found possible in any experiment t~ obtain any information as t o the molecular complexity of boron trioxide owing no doubt to I 178 MYERS BORIC ANHYDRIDE AND ITS HYDRATES. the very great velocity of the reaction between this substance and water. The next measurements made were those of the rate of dehydra-tion of orthoboric acid. It was found that a t the ordinary temperature orthoboric acid is not dehydrated when placed in a vessel containing phosphoric oxide.If mixed together dehydration takes place very suddenly a t a temperature between 8 5 O and 90°. Measurements of the rate of dehydration on heating were carried out by maintaining a weighed quantity of orthoboric acid at a constant temperature in an apparatus which allowed the free escape of water vapour as it was given off. The values obtained at' 103O are shown in table 111. TABLE 111. Orthoboric acid. Gram. 1 . . . . . . 0.337 2 . . . . . . 0.460 3 . . . . . . 0-459 4 . . . . . . 0.456 5 . . . . . . 0.464 Weight of Time in product. minutes. Gram. 52 0.257 34 0.387 20 0.415 74 0.320 85 0.329 The values obtained a t 1 3 5 O are given in table IV. TABLE IV. Orthoboric acid. Time in Gram. minutes. 0.582 5 15 35 65 134 Weight of product .Gram. 0-485 0.429 0.402 0-396 0.396 From the values given in tables I11 and IV the rate of (uni-molecular) reaction has been calculated and these values are shown in table V. TABLE V. Temperature Temperature 103" 135" k. k. 1 . . . . . . 0.014 0.074 2 . . . . . . 0.010 0.068 3 . . . . . . 0.009 4 . . . . . . 0.009 5 . . . . . . 0*008 The values for the dehydration at 1 0 3 O show a reasonable con-stancy but it was found that the loss in weight could not be satis GRAY A SIMPLE APPARATUS FOR THE WASHING OF GASES. 279 factorily explained in the cases of relatively long heating on the assumption that the product was metaboric acid and this fact introduces a small error in values (4) and (5). There seems to be a slow and continuous volatilisation of the product even a t this temperature.I n the case of heating at 135O it is only possible t o assume the formation of metaboric acid in t*he first two values, since the subsequent loss of weight cannot be accounted for on this basis. Up to the stage of metaboric acid the reaction seems to proceed in a similar manner to that at 1 0 3 O but after that stage has been reached there is evidence of the production of molecular complexes and in appearance the product is quite different from that obtained at. 103O. It is distinctly granular, and even slightly coloured. Holt has measured the vapour pressure of metaboric acid a t 180° but was not able to obtain evidence of the formation of definite compounds. Conclusions. (1) The hydration of boron trioxide takes place in at least two (2) The hydration to metaboric acid is very much faster than (3) The hydration of metnhoric acid is a unimolecular reaction. (4) The dehydration of orthoboric acid a t about looo proceeds as a unimolecular reaction t o Eetaboric acid. A t a higher temperature the reaction becomes much more complicated involv-ing probably the formation of molecular complexes of metaboric acid. stages first to metaboric acid and then to orthoboric acid. the further reaction. THE UNIVERSITY, MANCHESTER. [Received Pebruury 22nd 1917.

ISSN:0368-1645    

DOI:10.1039/CT9171100172

出版商:RSC    

年代:1917

数据来源: RSC