摘要:

THE ANALYST. AUGUST, 1891. EXPERIMENTS ON THE ESTIMATION OF BORIC ACID, BY OTTO HEHNER. (Read at iileeting, June 3rd, 1891.) THE separation of boric acid by means of distillation with methyl alcohol in an acid solution has been recognised by a number of investigators as being capable of securing rapid and accurate results, and certainly furnishes the readiest analytical meanq for the determination of boric acid in articles of food, The method is at present generally attributed to Gooch; but it seems to have originated somewhat earlier, or possibly inde- pendently, with T. Rosenbladt (Zeit. f. Anal. Chem., Vol. xxvi., p. IS), who distilled a sulphuric acid solution with methyl alcohol, fixed the boric acid contained in the distillate by the addition of a weighed quantity of magnesia, evaporating and igniting.Glooch, recognising that magnesia fixed boric acid only incompletely, or only after some hours of maceration, substituted for it caustic lime, a weighed quantity of which was placed in the receiver, the contents being afterwards transferred to a weighed platinum dieh, and the residue obtained by evaporation ignited over the blow-pipe. Penfield and Sperry (Amer. Jour. o f 8 c . xxxiv., p. 222), recognising the difficulty of igniting to constant weight a comparatively large quantity of caustic lime in a neces- sarily large platinum dish, modified the method by collecting the distillate, adding it to a weighed quantity of lime contained in a dish, evaporating, scraping out the contents of the dish into a weighed platinum crucible, dissolving adhering particles from the large dish with nitric acid, and adding the solution to the contents of the crucible, which is then ignited to constant weight.This method, clumsy as the tramference of a dry residue from one vessel to another must necessarily be, is improved by Cassal (ANALYST, Vol. XV., p. 230), who collects the distillate at once into a weighed platinum dish containing the lime; but this modification of the process does not remove the obvious difficulty of igniting upwards of a gramme of lime to a constant weight in a large platinum basin. I should here state that the use of lime for fixing boric acid is due to H. Gilbert (Repert. Anal. Chem., Vol. v., p. 375!, so that the Gooch method is really a combinatim of Rosenbladt’s distillation method and Gilbert’s ignition process.In order to substitute for the lime other substances capable of fixing boric acid, the investigation was undertaken, of which the results are recorded in this paper. Although some of my results are negative, yet they may be worthy of being brought before you, as clearing up certain points in the chemistry of boric acid about which some difference of opinion existed. Experiments to fix boric acid with ammonia. 0-4807 gramme of pure boric &id (H BO ) were placed in a weighed platinum dish, dissolved in water; ammonia was added, the solution evaporated, and the residue142 THE ANALYST. ~- - - - obtained first dried at 100’ C., afterwards ignited over an argand to constant weight. Residue at 100°C.. 0.4138, or 86.08 per cent.Ignited residue , , 0.2560, or 53.25 per cent. Theory for B,O, 56.45 per cent. 0.0898 gramme HsBO,, similarly treated with ammonia, yielded 0.0768 gramme at 100°C., or 85.52 per cent. This residue, repeatedly evaporated with ammonia, diminished steadily in weight to 0.0620, 0.0432, 0-0340, and 0.0263 gramme, or 34.2 per cent., at which point the evaporation was not continued, it being demonstrated that boric acid is volatile in presence of ammonia. This agrees with the observation of Bodewig (Zeit. fh. And, Chem., Vol. Xxiii., p. lag), who abates that upon evaporation of a solution of ammonium borate on the water- bath a point is reached at which the vapours were alkaline, but the liquor acid. Experiments to fix with sodium carbonate. It is well known that boric acid can be completely fixed by sodium carbonate; but the statements as to the amount of carbonic acid driven out by the boric acid are very contradictory.According to Bloxam, one molecule of boric acid displaces on gentle igni- tion one molecule of carbonic acid, but a t a strong red heat from 1.5 to 2.3 molecules; whilst according to Schaffgotsh one equivalent of H BO, expels all carbonic acid from two molecules of sodium carbonate. ade in this direction, any results of of sufficient accuracy for analytical purposes. To 0.5598 gramme pure boric acid (H,BO,), 2.7824 grammes dry pure Na2C0, were added, and the mixture heated to constant weight. The loss, including 43.55 per cent. of water yielded by the boric acid amounted to 102.03 per cent. of the boric acid taken, corresponding to 58.48 per cent.of GO,, or for one equivalent of H3B03, 0.824 of an equivalent of GOz. In a second experiment the loss amounted to 104.89 per cent., or 61.34 per cent. CO,, equal to 0.864 equivalents of GO2. As Bloxam’s statements are doubtless for the old equivalents, his figures become comparable by halving them, when they are 0.75 to 1.15. It is almost impossible to obtain constant weights, and I, therefore, abandoned the attempt. I could not obtain, in the few experiments I Experiments to f ; x with sodium phosphate. A solution of sodium phosphate was made, containing about 20 grammes pure crystallised sodium phosphate per lit re. 25 C.C. of this were evaporated, the residue first very gently heated over the smallest possible argand flame (to avoid loss by spurting), and then gradually over a large argand flame, the residue never being permitted to become red-hot.The residue weighed 0.1856 gramme. According to the fifth edition of L L Fresenius’ Quantitative Analysis,” at this temperature all water of crystallisation is driven off; but not consti- tutional water. This statement, however, is not correct, because on strong ignition of the above residue over a Bunsen flame, the weight remained perfectly constant. In the newest edition of Fresenius, I must add, this erroneous statement is omitted. 0,0632 gramme pure boric acid (H,BO,) was evaporated with 10 C.C. of the phos- phate solution, yielding 0.0742 Na,P,O,. The residue consisted of a perfectly transparent gummy mass, and was ignited most cautiously, as it is very apt fo spurt, over 8 smaQTHE ANALYST, 143 argand flame in a covered platinum basin, the heat being ultimately increased until the residue had fused.It weighed 0.1082 gramme, containing, therefore, 0.034 grammo B,O,, against 0.0356 B,O, taken, loss 0*0016. 0,0691 gramme H,BO,, corresponding to 0.0390 gramme B,O,, plus 2 0 C.C. phosph&e solution (0.1483 pyrophosphate), yielded 0.1863 gramme ignited residue, or 0.0380 This residue was evaporated with repeated quantities of water, in all 200 c.c.; the dry mass was again ignited ; loss of weight, none. O o l l O O gramme H,BO,, equal to 0,0621 gramme B,O,, was evaporated with 50 C.C. sodium phosphate solution (0.37 12 pyrophosphate), yielded 0.4340 gramme residue, or 0.0628 gramme B,O, +0*0007.0*1008 gramme H,BO,, equal to 0.0569 B,O,, evaporated with 35 C.C. sodium phosphate solution, containing 0.2598 gramme pyrophosphate, and then with 250 C.C. of distilled water in several portions. Ignited residue 0.3166, equal to 0,0568 B,O,; loss 0~0001. To ascertain the minimum quantity of phosphate necesaary to fix the boric acid a few experiments were made, which indicated, as far as they went, that one molecule of Na2HP0, is capable of binding 2 molecules of H3B0,, the resulting mass consisting OF sodium metaphosphate and borax. To 0,1785 gramme H,BO, a quantity of sodium phosphate was added, capable of yielding 0.1 91 6 gramme of pyrophosphate, this being the above molecular proportion. Residue obtained, 0.2894 gramme, or 0*0978 B,O, ; loss, OsO029.0.1792 gramme H,BO, (0*1015 B,O,) evaporated with 25 C.C. of water, without the addition of phosphate, and the residue ignited, yielded 0.0889 gramme B,O,, a loss of 0.0122 gramme, plainly showing the fixing influence of the sodium phosphate. To ascertain whether this was in any way affected by the presence of alcohol, 0.1606 gramme H,BO, (0.0906 B203) were dissolved in 100 C.C. methylated spirit, 150 C.C. water added, and a quantity of phosphate solution, yielding 0.3832 gramme pyro- phosphate; the mixture was then boiled in a covered beaker until all alcohol had evaporated ; the remainder was transferred to a weighed platinum basin, evaporated, and the residue ignited. The advantage of adding a soluble salt, which easily parts with its water, and which combines by direct addition with the boric acid to be estimated over a subsfance Eke lime, which incrustates the vessels and attracts carbonic acid, which is difficult to remove: is obvious.I am not sure that sodium phosphate is the best possible salt that could be chosen; but the results. yielded by its use are fairly satisfactory, and certainly very rapidly obtained. 1 only ascertained after the above analyses were completed that Stolba had long ago proposed to fix boric acid in solution by adding a weighed quantity of borax (about four times the weight), and igniting the residue (J0zcr.f. Prac. Chem., XC., p. 479). I have made experiments in this direction and find that very good results may be obtained, but that the greatest caution is necessary to avoid loss by crepitation during the ignition of the residue.Incidentally I may observe that boric acid cannot be alkalimetrically determined as no indimtor is at present known whioh allows of anything like a sharp titration ; BZO, - loss 0.0010. Obtained 0.4710, or 0.0878 B,O,, a loss of 0.0028.144 THE ANALYKI!. ~ and this inxpite of the curious fact that Guyard (Bud&. Xoc. Chem., xl., p. 422) has recommended pure crystallised boric acid as an alkalimetrical standard ; Iogwood, which he recommends as an indicator, fails utterly to yield a sharp colour change with the acid. I further wish to correct the statement found in books, that boric acid, when heated in a water-oven at 100OC. loses two-thirds of its water. Boric acid placed in a water-oven loses weight steadily, until the whole of it is volatilised, and no definite point at any stage can be observed.Thus 0.0736 gramme H,BO kept for three or four days a t looo C. diminished to 0.0179 gramme, or 24.3 per cent. of the original weight. This small residue ignited yielded 0.0108 B2OS, or 60.34 per cent. of its weight. If the residue had consisted of H2B204, as stated in the book, 72.7 per cent. ought to have remained. Of course, the deter- mination cannot be very exact, seeiog that it was made with a few milligrammes only; but the experiment proves sufficiently that by mere drying in the water bath no definite stage of composition can be reached. Lastly, I record the observation, that if anhydrous boric acid is dissolved in cold water, the turmsric reaction is not obtained, or, at least, only exceedingly faintly, in com- parison with an equivalent proportion of hydrated acid, whilst a strong reaction is at once obtained if a trace of mineral acid is added.This furnishes proof that boric anhydride dissolves as such, and does not immediately hydrate on being dksdved in water. The pieces of turmeric paper dried with solution of anhydrous boric acid gradually turn red when allowed to lie in the air of the laboratory. This observation suggests some interesting speculations, with the testing of which I am at prment engaged-namely, does there exist a series of pyroborates, just as there are pyrophosphates and pyrosulphates, and can their existence be analytically proved ? In the case of the phosphates, the colour of the silver salts at once shows the difference, whilst in that of the pyrosulphates, two reactions are due to E.Drechsel (J0ur.f. Piract. Chemie, v., p. 367), distinguishing pyro from acid sulphates. Anhydrous borax is, of course, pyroborate of sodium, Na2B,07 ; but all the reactions of borates are those of the ortho acid HsBOI, and ordinary borax is certainly the acid ortho salt. The difficulty experienced in rendering boric acid anhydrous renders it most unlikely that by Simple addition of soda in an aqueous solution, a molecule of anhydrous acid is produced, which combines with the neutral saIt Na2B,04. Borax according to this view would be Na2H2B,0, + 9 H,O, and boric acid H4B408 + HzO. The evidence that boric acid is tribasic is exceedingly slight. DISCUSSION, MR. BLOUNT said that Mr. Hehner's method was extremely ingenious ; but the objection to the lime process was not insuperable. He himself was in the habit of igniting lime to perfect causticity by the simple plan of using a muffle. It was the use of the blow-pipe, which he regarded as extremely unsuitable for this purpose, which caused all the trouble. MR. CASSAL said that the substitution of phosphate of soda for lime, in the method suggested by Mr. Hehner, was certainly a valuable improvement, since under the most favourable circumstances, to get the lime to constant weight was very troublesome. He desired to take the opportunity of stating that in itbatracts which had appeared of aTHE ANALYST. 145 paper read some time ago by himself, the introduction of methyl alcohol to separate boric acid had bsen erroneously attributed to him. He could confirm what Mr. Hehner had said about the turmeric test; it m& necessary to acid hydrochloric acid when dealing with anhydrous boric acid.

ISSN:0003-2654    

DOI:10.1039/AN8911600141

出版商:RSC    

年代:1891

数据来源: RSC

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THE ANALYST. 145 THE EFFECT ON BUTTER FROM FEEDING ON COTTON-SEED AND COTTON-SEED MEAL. BY N. T. LUPTON. (Journal of the American, Chem. Society, Vol. xiii., April, 1891.) AN investigation was undertaken a few months ago at the Alabama Experiment Station to determine the effect of cotton-seed and cotton-seed meal on the composition of butter- fat, especially on the volatile acids, the melting point, and the specific gravity of the butter produced. Several chemists of late years have calledattention t o changes produced by the use of the feed-stuffs mentioned, notably Prof, Harrington, of the Texas Experiment Station, and Dr. Wiley, of the Department of Agriculture, Washington, D.C. This siibject was thought to be of sufficient scientific and practical importance to justify an extended investigation.For this purpose, a herd of registered Jerseys was divided into two groups, one consisting of ten cattle and the other of a single cow, The cattle of the first group were fed for a preparatory pexiod of ten days on the customary ration used at t.he station, excluding cotton-seed meal and hulls, the single cow was fed on the same ration. At the end of the preparatory period, samples of milk and butter were taken for one week, on Monday, Wednesday, and Friday, and carefully analysed. The milk OF the ten cattle composing the first group was mixed and churned as a whole. That of the single cow was kept separate and churned by itself. The first preparatory period was for ten days; after that, the experimental and preparatory periods extended over seven days each.The daily rations for the different periods which represent the kind and quantity of food actually consumed, were &s follows :-- 1st period, preparatory and esperimental, Ground oats , . .. .. Ground corn . . .. .. Bran .. .. .. s . Nutritive ratio, . . a Cotton-seed meal , . .. . 1 Ground oats . . .. .. Bran .. .. .. .. Ensilage .. .. .. Nutritive ratio. . .. 2nd period. .. .. .. .. .. .. .. .. .. .. 5 lbs. .. 5 1 ) .. 5 Y Y 1:5*8 .. 3 lbt;.. .. 4 ?, .. 6 7 9 .. 11 ?? 1:3*75146 THE ANALYST. 1 Sugar, per cent, 3.96 5.09 5.24 6.1 9 5.98 5.12 6.03 5.19 5.0'6 5 22 5.37 5.16 5.08 5.04 - - 3rd period. Cotton-seed meal . . .. a . b. .. 4 lbf3. Cotton-seed hulls. . .* 0 . 0 . .. 9 9 , Ensilage .. 0 . .. 0 . * . 43 ?S Nutritive ratio .. e . 8 . 1:5.08 During the fourth period the cattle were confined exclusively to raw cotton-seed and cotton-seed hulla ; and during the fifth period to cooked cotton-seed and c o t t o n - 4 hulls; they were allowed as much as they would eat. The nutritive ratios mentioned above are calculated from analyses made of the feed-stuff8 in use at the station. In compounding the rations, the object was not so much to conform with strictneae to the German standard as to bring the cows gradually under the influence of cotton-seed, cotton-seed meal and hulls, without injury to their general health, The results of the analysis of samples of milk and butter, taken immediately after each milking and churning, are given below. The first two tablerJ give the composition of each sample of milk analysed, also the volatile acids, melting point and specific gravity of the butter from the same milk; the third table gives the average composition for each experimental period.Composition of Jersey Milk for each day analysed. Water. per ceni 85-76 84.95 84.1 5 83.62 84.26 84 53 83.35 84.71 84.27 84.59 84.51 85.84 84-89 85.38 - Butter F; per cent 5.53 5.20 5.73 5.51 5.1 6 5 96 6.07 5-79 6-41 6-11 5.84 4.87 5.95 5.53 Casein. per cent, 3.95 4.05 4.06 3-88 3.90 3,64 3.60 3l57 3:58 3.34 3-56 3.39 3.31 3.3 1 Ash. ?er cen *80 -81 98 2 * 80 40 *75 -75 -74 *73 *74 -72 -74 *77 *74 - Butter from same Milk. Volatile Acids. C.C. T'v normal .lkali for i grams. 30.0 29.6 29.7 30.5 31.4 28.4 26.9 27.1 22.0 21.9 22.4 23.1 22.2 22.1 - Melting point. CQ 35.9 35.3 36.0 36.3 36.1 36.6 37.6 38.1 43.6 43.9 43.4 42.7 42.3 43.0 jp.gr. a 1000 (3. -9026 a903 1 9041 ,901 6 ,9026 *go08 *9019 *go31 *go02 a8972 -8995 9046 09006 09027 - Rations. Period. 1 2 3 4 5 -THE ANALYST. 147 ~~ Composition OE Jersey Milk for each day analysed. Butter from same Milk. Melting point. :p. gr. a 1000 c. Water, Sugar. Volatile Acids, C.C. 1% normal alkali fo 6 grams. 31 *4 31.5 31-7 30 6 25.5 25.4 205 19.2 21.4 22 0 22 1 21.7 Rations. Period. 1 2 3 4 5 Ash. )er cenl *73 *8 1 *68 *71 -75 *72 *73 071 -69 *68 .70 -72 -7 1 Sutter Fz per cent 4.67 5.93 4.75 4.53 3.94 4.74 5.85 5.12 4.76 4.80 4.87 4-86 6.00 Casein, per cent 3.84 3.93 3-56 3.84 3.66 3.42 3-69 340 3.47 3.34 3.13 3.12 3.18 CQ 35.1 33.4 36.5 36.2 37-5 41.3 43.5 41.0 43.0 43.3 43-3 44.0 )er cenl 85.53 84.03 85.71 85.68 85.63 85.26 84-3 1 85.1 7 85.10 85.54 86.21 86.00 85.39 per cent 5.23 5.30 5-30 5 a24 6-02 5.86 5.42 5.60 5.98 5.64 5.09 5.28 4.72 *go19 *go46 *go28 *go02 -9019 *8980 -8975 *8993 *8988 -8977 *a999 *8980 ~~ ~ ~ ~~ Average Composition of Jersey Milk during each Period.Butter from same Milk. Water. I Period. Volatile Acids. Melting Point. - 35.6 36.1 37.4 4 3.6 42.7 34.2 36.3 39 I4 42.5 43.5 Sp. Gr. I t loOOC Butter Fa.t. 5.36 5.47 5.9 1 6.1 2 5.45 5.30 4.41 5.30 4.89 4.92 Sugar. I Rations. 1 2 3 4 5 1 2 3 4 5 Casein. 440 3.95 3.60 3.49 3.36 3.89 3.69 3.37 3-40 3.14 Ash. *8 1 08 1 -7 5 -7 3 -75 -77 071 *72 *69 *71 I- Group I. I. 11. 111. I v. V. 85-36 84.0 1 84.20 84.46 85.37 4.52 5.80 5.45 5.20 5-09 5.26 8.52 5.64 5-74 5-03 2 9.8 30.5 27.5 22.1 22.5 31.4 31.1 25.45 20.4 21.9 ,9028 *go28 -9019 -8990 -9026 *go32 09015 -8999 -8986 08986 Croup IT. I 11.111. IT. V. 84-78 85.67 844'9 85*27 85.87 The following table, taken from a record carefully kept at the dairy, gives the148 THE ANALYST. aggregate amount of milk and butter produced by the first group, consisting of ten cows, for each experimental period of seven days :- Pounds of Milk for 1 lb. of Butter. Founds of Milk. Pounds of Butter. Period I .. 14144 .. 82 .. 17-2 2 .. 1275 .. 854 .. 14.9 3 .. 975 .. 91 .. 10.7 4 .. 896 .. 75 .. 11.9 5 .. 716 .. 58 .. 12.3 As will be observed, there is a marked falling off in the quantity of milk and a corresponding increase in the amount of butter produced during the first three periods, as the cattle were getting more under the influence of cotton-seed meal.During the remaining periods, the quantities of both butter and milk diminish, the ration being confined to cotton-seed and cotton-seed meal, without reference to having i t well balanced as a milk ration. The general effects of these valuable feed-stuffs, when used in carefiilly prepared rations, will hereafter be investigated. At pressnt we are concerned only, as previously stated, with their effects on the volatile acids, melting point and Bpecific gravity of the butter-fat produced under their influence. For these effects attention is called to the above tabular statements, from which the following conclusions are drawn :-Feeding on cotton-seed and cotton-seed meal increases, in a marked degree, the melting point of butter, the increase reaching in these experiments eight or nine degrees, and diminishes t q a corresponding extent the volatile acids, while the specific gravity remains virtually the same. The richness of cotton-seed meal in albuminoids renders it of prime importance to mix it with one or more food-stuffs poor in this nitrogenous compound, such as ensilage, hay, or cotton-seed hulls. It may be stated in this connection, that no change was observable in the colour of the butter from feeding with cotton-seed and cotton-seed meal. The samples, still in the laboratory, are all of a beautiful golden yellow. It is proper to state that the analytical work in the above tables waa done by Dr. J. T. Anderson, first assistant in the chemical laboratory.

ISSN:0003-2654    

DOI:10.1039/AN8911600145

出版商:RSC    

年代:1891

数据来源: RSC

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148 THE ANALYST. THE ANALYSIS OF BEESWAX. C. MANGOLD. (Chew. Zeit. 1891, 15, 799,800.) ON account of the natural fluctuations of the so-called constants of yellow beeswax, such as the acid and saponification numbers, &EL well as the iodine number determined by the Hub1 process, adulteration with less than 6 per cent. of paraffin or ceresin is dif5cult to detect. A. and P. Buisine, applying (Bull. Soc. Chm. 1890, 3, 667) the principle previously enunciated by Hell, Sturcke and Schwalb, have devised a method of sufficient apparent value to warrant its investigation a t the hands of the author. The wax is saponified with potash and heated with potash lime, by which treatment the higher alcohols are converted into fatty acids with elimination of hydrogen, which serves as a measure of their amount.The hydrocarbons present are unattacked and can be extracted from the residue. The author’s investigations confirm those of A, and P. Buisine, and have led him toTHE ANALYST. 149 ~ ~ ~~ recommend the following method :-2-10 grammes of the wax are melted and saponified by potash-lime, the reaction being aided by stirring. The saponified product is powdered when cold, intimately mixed with three times its weight of potash-lime, and the mixture transferred to a thick-walled, pear-shaped bulb-tube, which is heated to 250° C. (for two hours according to Bhisine, *c$, the time adopted by the author below) in a mercury- bath contained in an iron vessel. This vessel is provided with a lid which screws on air- tight, pierced with four apertures through which pass air-tight, respectively, the pear-shaped bulb, a thermometer, a thermostat, and a long tube open a t both ends to condense any mercury which may volatiliee.A tube connects the pear-ahaped bulb with a Hofmann’s burette, in which the hydrogen is measured. Although the author has made some determinations of its amount (obtaining resulta somewhat lower than those of Euisine), his attention has been chiefly directed to the estimation of the hydrocarbons present. Having observed, however, that the volume of hydrogen only becomes constant when the heating has h e n continued for three hourg, he adopts this time ag the minimum necessary for the determination of the hydrocarbons. After the completion of the reaction, the residue in the bulb-tube and the bulb-tube itself are powdered and extracted for some hours with petroleum ether in a Soxhlet’s tube, the ether distilled off, and the residual hydrocarbon dried at l l O o C.and weighed. Schwalb has already noted (Annulen, 1886, 235, 149) that pure beeswax itself con- tai-as about 6 per cent. of hydrocarbons ; while A. and P. Buisine have found as muGh as 12-5-14 per cent., a result confirmed by the author. In endorsing this statement, he arrived at the conclusion that as little as2 per cent. of foreign hydrocarbons may be detected. The best approximation to the true proportion of paraffin is said to be obtained by assuming the quantity of hydrocarbons normally present in beeswax to be 13.5 per cent. The following table gives some figures for unbleached beeswax of diverse origins :- Source of sample.Aussee . . .. Native . . .. Dalmatia . . .. Hungary .. .. Bosnia (Banjaluka) Slavonia . . .. Carniola . . .. Bosnia (Dolna-Tulza) Lower Styria . . Lower Austria . Mozambique . . Chili .. .. MonteCristo .. Morocco . . .. Bombay .. .. Madagascar .. .. .. 9 , Saffi .. .. Oran .. .. Massanah . . . * Mogador . . .. .. .. .. .. .. .. .. .. .. .. * * .. .. .. .. .. .. .. .. .. .. Hydrocarbons, 13-51 13.75 14 72 14.51 14.60 14-27 13.76 13.64 13.32 14.34 1372 13.37 13-35 :I 3.50 11 *02 14.04 11-77 12.20 11.55 12.80 11.40 Acid number. 19.79 20-44 20.42 18.81 23.04 19.31 20.95 20.08 20.02 18.26 20.58 19-42 19.99 20.24 21.66 20.03 19.92 19.91 21.11 20.85 .- True saponification lumber (after deduc- tion of acid number.) 72.51 70.65 67.84 71.99 66.55 70.23 69.62 70-37 72.50 67.83 71.78 70.01 67-45 77.02 72.85 73.48 79.99 69.49 75.65 c -150 THE ANALYST, Source of sample._- _I A sample of yellow beeswax from Transylvania had an acid number of 16.66, and a total acid number of '72168; thatis to say, a true saponification number of 56.02, plainly indicating that it was adulterated with paraffin or some similar hydrocarbon. The total percentage of hydro-carbons was 28.12, corresponding to an addition of 17 per cent, of paraffin calculated on the original wax. The percentage of hydrocarbons and the total acid number of the mixture being known, the total acid number of the original wax could be calculated, and was found in this case to be 8'7.6. A mixture made by adding 8 per cent. of paraffin to a genuine sample of beeswax gave flgures on analysis corresponding t o an addition of 7.4 per cent. A few figures for bleached beeswax are also given. ' True saponification Hydrocarbons, Acid number. number (after deduc- tion of acid number). Smgrna . . .. . z Egypt * ' .. .. Transylvania . . I . Hungary ., .. ' * I 10.93 11.35 13.61 15-48 20.87 20.04 24.68 23-05 68.33 69.94 "79.49 - i I I According to A. and P. Buisine, bleached wax gives a lower result for hydrocarbons than yellow wax ; the last two samples are apparently impure, and have been bleached by chemical means. B. B.

ISSN:0003-2654    

DOI:10.1039/AN8911600148

出版商:RSC    

年代:1891

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150 THE ANALYST. A NEW TEST FOR ALBUMEN AND OTHER PROTEIDS. BY J. A. MACWILLIAM. (From Cliem. and Drug. after B. Ned. Jozcrm.) THE test employed is salicyl-sulphonic acid (C,H,.OH.SO,H.COOH), which is made by the action of sulphuric anhydride on salicylic acid, or by heating salicylic acid with con- centrated suIphuric acid. The product is an exceedingly delicate and precise test for the detection of allproteids in solution, the presence of which it reveals by the formation of a dense white precipitate, which becomes flocculent on heating. Various substances classed under native albumens, derived albumens, globulins, fibrin, albumoses, and peptones have all been tried, and all respond to the test; but the precipitates of albumoses and peptones are redissolved on heating, which distinguishes them from albumens and the like.The test is applied by adding a few drops of a solution of the acid to the solu- tion of the proteid. The precipitate forms at once, or, in tho case of very dilute solutions, within one minute a cloudiness appears. To give some idea of the delicacy of the test Professor MacWilliam provides data, of experiments. From these we note that a soh- tion of egg albumen, 1 in 2,000, gave no reaction on boiling in presence of excess of acetic acid. A 1 in 8,000 solution also failed t o respond to the xantho-proteic, Heller’s, and the mercuro-potassic iodide tests, although it gave a distinct opalescence with the salicyl-sulphonic acid test-indeed, the same was obtained with a 1 in 12,500 solution. It * 74.49 in original.THE ANALYST.151 was applied to other proteids with equally satisfwtory results. The test is, of course, intended for the detection of albumen in urine. In view of the number of substances which may occur in that fluid which might react with the test, Professor MacWiIliam gives results of careful experiments, which show that (1) the precipitate is a proteid one ; (2) it is always obtained when proteid is present in the various abnormal conditions of urine; (3) it is not given by non-proteid substances, such as phosphates, urates, much, the alkaloids, and drugs generally; (4) for delicacy and precision it surpasses all other tests; the only one approaching it is the mercuro-potassic iodide test, and this gives copious precipitates with alkaloids and other substances, It is evident that the test is one of great delicacy for the detection of albumen in urine, and, as it is more easily performed than even the simple boiling test, it will doubtless rapidly become popular.Take a small amount of urine (for example, 20 minims), preferably in a very small test-tube, and add a drop or two of a saturated watery solution of the reagent. If the urine is strongly alkaline, an extra drop or two of the acid should be added, and if no opalescence or precipitate occurs it is well to test the reaction with litmus-paper, and make sure that the urine has been rendered strongly acid. On adding the reagent, shake the tube quickly so as to mix its contents. The occur- rence of an opalescence or cloudiness immediately or within a very few seconds (for example, two or three seconds) is a test for proteids intermediate in deIicacy between the cold nitric acid test on the one hand and the acetic acid and heat test (in favourable circum- stances) on the other.The development of an opalescence some time after (one-half t o two minutes) is a more delicate test than even acetic acid and heat, and shows the presence of minute traces of proteid, which are probably insignificant, from a clinical point of view, as a rule. If the precipitate or opalescence is caused by the ordinary (( albumen " (albumen and globulin) commonly present in albuminous urine, it does not disappear on heating, but, on the other hand, becomes markedly flocculent. But if the precipitate or opalescence is due to the presence of albumoses or peptones, it clears up on heating (before the boiling point is reached) and reappears when the tube cools. Salicyl-sulphonic acid, or sulpho-salicylic acid, occurs in colourless, long, thin, needle- shaped crystals, which are very soluble in water, and melt a t 120" C. It must not be confounded with salicyl-sulphuric acid ( C,H4.S0,H.COOH). Salicyl-sulphonic acid is best made by heating salicylic and sulphuric acids together, allowing the new-formed acid to crystallise out, collecting and recrystaliising from warm water. The acid gives an intense reddish-violet colour with ferric chloride. The manner of applying the test is as follows :- Then examine a t once. Next heat the tube to the boiling point.

ISSN:0003-2654    

DOI:10.1039/AN8911600150

出版商:RSC    

年代:1891

数据来源: RSC

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THE ANALYST. 151 ANALYSIS OF GREY COPPER ORE, ETC. BY W. HAMPE, ( C h c m i b Zsitzcng, No. 26, 1891.) FOR dhsolving minerals or metallurgical products which contain arsenic, antimony and perhaps tin, the best plan is to use a mixture of nitric and tartaric acids. This152 THE ANALYST, has the advantage over nitro-hydrochloric acid, or hydrochloric acid and chlorate of potash, or bromine water, as there is no need for any precautions to prevent volatilisation of arsenic. It has the advantage over nitric acid alone, that there remains no residue of antimonious or stannic acid contaminated with lead or copper, which, of course, greatly simplifies the analysis. The tartaric acid must first be tested as to its purity. The watery solution must not be precipitated by hydrogen sulphide (absence of lead, tin) or rendered turbid by ammonia and ammonium sulphide.For one gram. of the mineral, grey copper ore, for instance, I use 10 grams of tartaric acid and about 30 C.C. of nitric acid, and allow the mixture to stand for some hours in a warm place. If the sample contains no, or but little, sulphur, it dissolves clear, but there generally remains a little undissolved sulphur. This must be filtered off and treated with warm solution of potassium sulphide. The obtained is kept and afterwards united with the main solution of the sulphides of arsenic, antimony and tin. If the potssium sulphide should leave a residue consisting of un- decomposed mineral, this should be again treated with the acid mixture and the solution obtained added to the first filtrate.This liquid is now heated up to 60° C, and saturated with hydrogen sulphide. After standing for twelve hours, it is again treated with the gas until it is certain that every trace of arsenic is deposited. The precipitate is then filtered off and extracted in the usual manner with potassium sulphide, the resulting solution of arsenic, antimony and tin filtered off, and those metals reprecipitated by dilute sulphuric acid. After filtration their sulphides are dissolved off the filter by means of freshly- prepared ammonium sulphide, and this solution evaporated nearly to dryness. Hydro- chloric acid and potassium chlorate are now added, and when all is oxidised, some tartaric acid. After addition of ammonia, the arsenic is thrown down with magnesia mixture. The magnesium ammonium arseniate is freed from any tartrate by redissolving in hydrochloric acid and reprecipitation with ammonia.If the amount is small, I dissolve it in nitric acid, evaporate the solution and finally gently ignite the residue to convert it into magnesium pyro-arseniate; but if large, I operate as follows:- The precipitate is again dissolved in hydrochloric acid, the liquid freed from arsenic by means of hydrogen sulphide, and after concentration, precipitated by ammonia and sodium phosphate. The magnesia is finally converted in the usual way into pyro-phosphate. The united filtrates of the ammonium magnesium arseniate are acidified and treated with hydrogen sulphide to throw down the tin and antimony, which are finally separated by Rose’s process.As regards the treatment of the precipitate which is insoluble in the potassium sulphide, I have nothing important to add. The filtrate from the hydrogen aulpbide precipitate must, as it contains tartaric acid, be precipitated by ammonia and ammonium sulphide to throw down iron, cobalt, nickel and zinc, These are then separated by the usual methods. To estimate the sulphur, 1 gram of the sample is fused in a platinum crucible with 6 grams. of nitre and 6 grams of dry soda, the mixture being covered with a layer of nitre. The mass is extracted with water, and any lead removed by a current of carbonic acid. After evaporation with excess of hydrochloric acid, the raulphur ia precipitated as usual with barium chloride. The presence of tin does not interfere.THE ANALYST, 153 A Modification of the Reichert Distillation Process.H. Leffmann and W. Beam (a pamphlet*).-In order to obviate entirely the use of alcohol in the saponification of butter and other fats, the authors adopt the following mode of pro- cedure :-The saponification is effected by a mixture prepared by adding 25 C.C. of a clear 50 per cent. solution of sodium hydroxide to 125 C.C. of pure glycerine, and boiling for fifteen to twenty minutes to evaporate the greater portion of the water. About 5 grammes of the clear fat are weighed out in a flask in the usual manner, 10 C.C. of the alkali-glycerine added, and the flask heated over a Bunsen burner, The mixture may foam somewhat ; this may be controlled, and the operation hastened by shaking the flask.When all the water has been driven off, the liquid will cease to boil, and if the heat and agitation be continued for a few moments complete saponification will be effected, the mixture becoming perfectly clear. The whole operation will require less than five minutes. The soap is then dissolved in 90 C.C. of water. The first port.ions of water should be added drop by drop, and the flask shaken between each addition in order to avoid foaming. When the soap is dissolved, 50 C.C. of diluted sulphuric acid (25 C.C. of the concentrated acid to the litre) are added, a piece of pumice dropped in, and the distillation conducted as usual. Blank experimenfa have given the authors a distillate requiring from 0-2 to 0.3 C.C. decinormal alkali. The alkali-glycerine is quite viscid when cold.It should be kept in a flssk closed with a rubber stopper, and heated when the measured portion is to be taken. 0. H. On the Digestibility of the Albuminoids of Cocoa. A. Stutzer. (2eitschr.f. Angew. Chem. 1891, p. 368.)-The value of cocoa as a food is not unfrequently over-estimated. Its nitrogenous substances consist of ammonia, theobromine, amides, and albumen, part of which is digestible, part quibe indigestible. The non-proteids are soluble in neutral, aqueous solution in presence of cupric hydrate, the proteids being insoluble under these conditions. I n 1 gramme the total nitrogen is estimated by Kjeldahl. For non-proteids 2 grammes are mixed with cupric hydrate and washed with cold water, and from the filtrate the ammonia is liberated by magnesia and distilled off.Cocoa-powder, partly deprived of its fat, contains only traces, certainly less than 0.1 per cent. of nitrogen as ammonia, unless ammonia has been employed for the purpose of rendering the cocoa soluble, The theobromine is determined by boiling out 20 grammes of the sample, precipitating the albuminoids from the solution with ferric acetate, and in the filtrate the theobromine by phospho-tungstic acid, the nitrogeo b i n g estimated in the precipitate. The difference in soluble nitrogen is calculated into amides. Theobromine nitrogen multiplied by 3.15 = theobromine, amide nitrogen by 6-25 = amides. The indigestible albumen is determined by digesting a weighed quantity of the powder first with an acid pepsine solution, then with an alkaline one of pancreas.The matter remaining insoluble is filtered off and Kjeldahled. To obtain exact determinations it is advisable previously to remove all the fat from the sample by ether. The author found in four samples the following amounts of albuminoid nitrogen : * 716, Walnut Street, Philadelphia.154 THE ANALYST. Nitrogen in solublealbumen . . 1-64 1-23 1.68 1.2 Nitrogen in insoluble albumen 1.15 1.47 1-23 1-28 For every 100 parts of digestible albumen the eamples contained indigestible nitrogen , . 70 119 73 103 That much of the nitrogen becomes indigestible by the roasting which cocoa undergoes during the process of manufacture is shown by the following figures obtained from the unroasted cocoa beans, While of the total nitrogen of the eamples of cocoa powder just referred to 31.2, 44.5, 31.2, and 35.8 per cent.were insoluble, samples of Ariba Machala, and Bahia cocoa beans, without shell, had only 23.2, 22.8, and 19.3 indi gestible, and the same beans roasted 39.7, 40.3, and 40.3. 0, H. On Certain Points in the Estimation of Barium as the Sulphate. F. W. Mar (Journal of Analytical und Applied Chemistry, vol. v., p. 278).--The author finds, as is well known to most analysts, that barium sulphate comes down in a strongly hydrochloric acid solution in a much more granular and filterable condition than from a slightly acid one. He studied the influence of the acidity on the solubility of the sulphate. From a solution containing in 400 C.C. 0.5 gramme barium chloride and amounts of hydrochloric acid varying from 1 C.C.to 5 C.C. the barium was precipitated by means of 10 C.C. dilute sulphuric acid with 10 C.C. to 15 C.C. of hydrochloric acid. The pre- cipitate settled clear in ten to twelve minutes, and was in excellent condition for filtra- tion. It is well known that barium sulphate is very apt to carry down with it consider- able quantities of alkaline salts, from which it must be purified, generally, by heating with hydrochloric acid after ignition of the precipitate. The author gives the results of a number of experiments in which he dissolved the barium sulphate by heating it with strong sulphuric acid in a porcelain basin, then driving off the acid over a small argand flame, when sandy crystals of barium sulphate are obtained, which are perfectly free from alkaline salts, and can readily be washed and weighed.The loss under these circumstances amounted to only about 0.4 milligramme. 0, H. On the Iodine Number of Lard-Oil by the Hub1 Method. Reuben Haines (Journal of Analytical and Applied Chemistry, vol. v., p. 287).-Three samples of lard, stated to be pure, were examined. Two of these were factory lards, and had a melting point of 45"C., whilst a country lard melted a t 33O C. The iodine numbers of these samples were 62-30, 62.49, and 59.33 respectively. The oil was then pressed out of the samples by means of a hand drug-press, at a temperature between 45W. and 65OC. Their iodine numbers were 74-14, 73-03, and 70.01 j average for oil from both factory lards, 74.0; average of the three, 72.7. The free fatty acid amounted to 0.86, 0.49, and 1-35.The samples gave no silver reaction. A sample of prime lard-oil, guaranteed by the dealer to be pure, had an iodine number of 74-0, and a Maumen6 of 42, the experiment being made in the manner recom- mended by Allen. 0. H. The oils thus obtained began to solidify at about 45OC.THE ANALYST. 155 Detection of Rosin Oil in Fatty and Mineral Oils. A. Grittner (Zeit: fiir angewadte Chemie. May, 1891).-The author of the paper describes a seriw of test experiments undertaken with a view to ascertain the sensibility of several processes which have been proposed for this purpose. He finds the original process proposed by Storch (Ber. Ost. G., 1887, p. 93) has only a limited application ; since when the oil is dissolved in acetic anhydride and sulphuric acid added, train oil gives a red colour, and the cholesterin present in many fatty oils produces a violet one.With dark-coloured mineral oils, the violet colour produced by the sulphuric acid is completely masked by the deep colour of the oil. This process was modified by Morawsky, who, instead of adding strong sulphuric acid to the solution of oil in acetic anhydride, used an acid of 1.53 s.g. The colour produced is the same as with the original method of Storch-a violet red. Holde (M. Vers. Berlin, 1888, p. 88), used originally an acid of 1.53 sag., with which rosin oil gives a red colour; later (&C. Cit., 1890, p. 19.) he increased the strength of his sulphuric acid to 1.624 s.g., since he found that with some rosin oils the colour was only produced with the weaker acid after prolonged shaking.The rosin oils examined by the author gave Morawsky’s original reaction, and Holde’s original and modified one, the only difference being that, with Holde’s stronger acid, the colour appeared immediately, whilst with the weaker acid it was necessary to shake for some time before the colour appeared. Quite black rosin oils did not give Morawsky’s reaction so characteristically as was observed with lighter coloured oils. In mixtures of rape and rosin oils in varying proportions the limit of sensibility of Holde’s original and modified processes was found to be about 1 per cent. ; whilst with Morawsky’s process $ per cent. could be detected with certainty. If rape oil be shaken with sulphuric acid of 1.53 s.g.the colour of the deposited acid is little altered, at most t o a pale yellow ; but if the same oil be treated with acid of 1.624 sg., the acid is coloured dark yellow. With mixtures of up to 1 per cent. of rosin oil, the 1.53 s.g. acid gives a red colour, whilst the 1.625 s.g. acid gives an orange red one. The author prefers the colour produced by the weaker acid, as being the more characteristic one. Train oils before being tested for rosin oil must be shaken out with alcohol; the alcoholic solution when settled can then be tested for rosin oil. The reaction will be best observed by allowing the sulphuric acid to trickle down the side of the vessel ; if rosin oil be present, a red or violet ring will be formed at the place of contact. The author finds with light-coloured train oils mixed with a small percentage of rosin oil Morawsky’s method is the preferable one ; with dark-coloured oils Holde’s method is the best.Morawsky’s method is inapplicable in the case of the dark mineral oils used for lubrication purposes. Since resins-colophony, shellac, etc., give a similar reaction, the absence of these bodies must be ascertained. In such cases it is necesaary to saponify the oil, and to test the unsaponifiable portion. For dark mineral oils i t is advisable t o use sulpliuric acid of 1-53 sg., which, at most gives a slight yellow colour ; many mineral oils treated with a stronger acid give a dark yellow colour, which interferes with the sharpness of the reaction. The author considers the method with acid of 1.53 the preferable one; the rosin oils investigated by him gave the reaction just as sharply with the weaker acid as with the stronger .156 THE ANALYST.- The author now investigated the action of syrupy phosphoric acid on train and mineral oils. Schoedler" states that train oil mixed with syrupy phosphoric acid 5 to 1, gives a red colour passing into dark red, which is readily observable in dilutions of 1 per cent. The author denies this, since he obtained not a red, but a dirty brown colour, and this evm only after prolonged shaking. Train oik, of undoubted origin, treated with syrupy phosphoric acid, prepared exactly according to 8chaIlen's directions, show only a very weak red colour, which does not increase on prolonged shaking. Holde obtained with rosin oil and phosphoric acid an orange to blood-red colour j the rosin oils, investigated by the author, however, gave colours varying from violet-red to brown- red.Since the colours produced with phosphoric acid are different, no qualitative reaction can be based upon them ; nevertheless the author has determined ita sensibility. In mixtures of rosin oil with rape or mineral oils, it was found that sometimes 5 per cent. could be detected ; at other times it could not j the difference evidently depending npon the quality of the rosin oil. The phosphoric acid process is therefore very much inferior to those of Morawsky or Holde. w. J. f3. The IOdOrn8triC Estimation of Nitric Acid Tn Nitrates. George McGowan (Jour. Chem. Xociety, July, 1891, p. 530).--This process is similar in prin- ciple to the one described by De Koninck and Nihoul (Zeit.f. angew Chernie, August 15, l890), but the details of the methGd and the apparatus employed are very different . When a fairly concentrated solution of a nitrate is warmed with an excess of pure, strong hydrochloric acid, the nitrate is completely decomposed according to the following equation :-HNO, + 3 HCI = NOCI + C1 + XH,O, the chlorine being evolved quantita- tively. If the operation is conducted in an atmosphere of carbonic dioxide, and the escaping gases are passed through a solution of potassium iodide, an amount of iodine is liberated exactly equivalent to the whole of the chlorine present (free and combined), nitric oxide escaping. One molecule of nitric acid thus yields 3 atoms of chlorine or iodine.The iodine is titrated in the usual manner with sodium thiosulphate. Absolute exclusion of air from the apparatus is necessary, since if present the nitric oxide would be oxidised to higher oxides of nitrogen, which would liberate a further quantity of iodine. The following is a description of the apparatus used :-The main point to be attended to is to have no corks or rubber stoppers, etc., for the escaping chlorine to act upon. The form of the apparatus is shown in the accompanying cut ; the condensing arrangement for the chlorine works perfectly, and may be used with advantage in other analytical processes in which iodine is set free. The measurements given are those of a conveniently-sized apparatus.THE ANALYST. 16’7 A is a small, round-bottomed flask, into the neck of whicb a glass stopper x is accurately ground.The capacity of the bulb is about 46 c.c., and the Iength of the neck, from x to y, 90 mm. The first condenser is a simple tube, slightly enlarged at the foot into two small bulbs (compare Sutton’s 4i Volumetric Analpig,” fourth edition, p. 103). The capacity of the bulb (B) is 25 c.c., and the total capacity of the two bulbs and tube, up to the top of C, 41 C.C. This condenser is immersed, up to the level of c, in a beaker, full of water. D is a Geissler bulb apparatus (Dittmar’s modification), and E a chloride of calcium tube, filled with broken glass; g is a small funnel, attached by rubber and clip to the branch T-tube h ; between tho T-tube (i) and the wash- bottle for the carbonic dioxide is placed a short piece of glass tubing (s), containing a strip of filter paper, siightly moistened with iodide of starch solution. This tube (s) is hardly necessary, as no chlorine escapes backwards if a moderate current of carbon dioxide is kept passing.The joints (0, p, q), of narrow india-rubber tubing, practic- ally expose no rubber to the action of the chlorine j k is the outlet tube. The actual operation is performed as foIlows:---The nitrate (say, about 0.25 gramme potassium nitrate) is introduced into the clean and dry evolution-flask, 1-2 C.C. water added, the bulb gently warmed to dissolve nitrate, and stopper firmly inserted in flask. About 15 C.C. of a solution of potassium iodide (1 to 4) are run into the first condensing tube, any iodide adhering to the upper portion of the tube wwhed down with a little water; 6 c.c iodide solution mixed with 8-10 C.C.water are sucked into the Geissler bulbs; the broken glass in E is thoroughly moistened with the iodide, The Geissler bulbs are arranged so that gas only bubbles through the last of them.158 THE ANALYST. All the joints being tight, the carbon dioxide is turned on briskly until all air is removed from the apparatus. The small outlet tube ( I ) is now replaced by a chloridh of calcium tube, filled with broken glass moistened with the above iodide solution, and closed by a cork khrough which an outlet tube passes, the object of this 6‘ trap ” being to prevent any air getting back into the apparatus, and a brisk current of carbon dioxide again pawed.The stream of gas is now stopped for an instant, and about 15 C.C. pure, chlorine-free hydrochloric acid run into A through the funnel g (into the tube of which it is well to have run a few drops of water to displace air), and A is shaken to mix its contents thoroughly. A slow current of carbon dioxide is now turned on (1-2 bubbles through the wash-bottle per second), and A is gently warmed. It is distinctly advantageous that the reaction does not begin until the mixed solutions are warmed, when the liquid becomes orange-coloured, the colour again disappearing after the nitrosyl chloride and chlorine have been expelled. The warming should be very gentle at first to make sure of the cmversion of all the nitric acid, and also because the first escaping vapours are relatively very rich in chlorine; afterwards the liquid in A is briskly boiled. When the volume of liquid in A has been reduced to about 7 C.C.or so (by which time it is again colourless), the stream of carbonic dioxide is slightly quickened, and the apparatus allowed t o cool down a little. About 2 C.C. of warm hydrochloric acid are run in gently through g; there is no fear of the iodide solution running back, or of any bubbles of air escaping through y if this be done carefully. The carbon dioxide is once more turned on slowly, and the liquid in A boiled until reduced to about 5 C.C. It is now only necessary to allow the apparatus to cool down, passing carbon dioxide all the time, after which the contents of the condensers are transferred to a flask and titrated with sodium thiosulphate.At t4e end of a properly-conducted experi- ment, the glass in the upper part of E should be quite colourless, and there should be only a mere trace of colour in the lower part; the liquid in the last bulb of the Geissler apparatus ought to be only pale yellow. During the operation it is well to test the stopper and also various joints for tightness with a piece of iodide of starch paper j also, before disjointing, to test the gas escaping at m, to make sure that all nitric oxide has been expelled. The following test experiments are given :-Ot finely-pawdered pure potassium nitrate, dried at about 160°C.*, 0.2627 gramme gave 0.2624 gramme, or 99.89 per cent. 0*2990 gramme gave 0.2992 or 100.08 per cent. An analysis of a commercial nitrate of soda gave the following results :- Moisturo at 16OoC... .. *. NaNO, .. I . .. .. .. .. . . 94.68 )) )) NaCl .. .. .. .. .. .. . 1.55 )) Na,SO, . . .. .. .. .. .. . 0.44 )) )) Insolubl0 matter (ignited) . I . 0 . . . 0.41: ,, ,) 0 . , , 2.95 per cent. 100*06 The author made a number of experiments with the addition of manganese * The author finds the moisture of commercial nitrate of soda is not completely driven off at the temperature of an ordinary air (water 1) bath (about 91iQC.).THE ANALYEIT. 169 aulphate aa an intermediary j and though fairly amurate results were obtained in this way, he finds the process acts better without any addition of this kind. The process is only applicable in the absence of organic matter and reducing age& generally.There are two slight errors involved in it which neutralise one another-the difficulty of getting rid of the last traces of air in the carbon dioxide generated in a Kipp apparatus, and the slight loss by volatilisation of iodine in transferring the iodide liquid to the flask for titration. A strongsolution of potassium iodide should therefore be used. The nitric oxide is apparently completely driven out of the apparatus in a properly conducted experiment. The presence of nitric oxide in the fluid to be titmted may be readily detected by the blue colour returning immediately after the solution has been decolourised by thiosulphate. A fifth-normal thiosulphate solution (50 grammee per litre) was found the most convenient strength to work with, 0-25 potassium nitrate requiring about 38 C.C. of such a solution.Advantages of the process are :-rapidity and simplicity. W. J. S. Determination of Nitrates in Water. A. Hazen and H. W. Clark (Jourrt. of Anal. and AppEed Chem., Vol. v., p. 301).-The phenol-sulphonic acid process, which essentially consists in the evaporation of a measured portion of the wafer to dryness, treating the residue with a solution of phenol in sulphuric acid and rendering the solu- tion strongly alkaline, the yellow colour produced being compared with that obtained in a similar manner from a known quantity of nitric acid, was carefully investigated. The best results are obtained with about 1 C.C. of a 5 p.c. solution of strictly pure phenol in sulphuric acid, nearly free from water, added to the residue and without warming.Caustic soda was substituted for ammonia for rendering alkaline. Attempts to use standards made from pure picric acid proved entirely unsuc~888fu1, the colour being only one-third as deep as that made by treating potassium nitrate with phenol-sulphonic acid. Other nitro-phenols were tried, but none matched $he staodards perfectly. It was recognised that in the solutions prepared from potassium nitrate, a mixture in varying proportions of different nitro-phenols was obtained. These have not the same colour for equal contents of nitrogen, and the authors were unsucceMful in so controlling the reaction as to get a constant product, or in finding a Substituted phenol with which there can be only a single nitro-compound sufficiently soluble in water or otherwise adapted for the purpose. The results of the process upon 150 ground waters averaged 11 p.c.lower than the results obtained by reduction by the aluminium method. In some instances the chlorine was removed from the water with silver sul- phate ; although the results in these cases were somewhat higher, yet they were deficient. The authors conclude, that while the process may be useful in some cases, the results generally are not of the requisite accuracy. 0. H, Volumetric Estimation of Phenol. Meissinger and Wortmann (Phccrm. Zeit. f. Rusdand, xxix., p. 759, through Jozcrm. de €'harm. Brzca8ek, Vol. xlvii., p. 244).-The process is b w d op the property possewed by iodine of eontbiniagI60 THE ANALYST. ~ with phenol in alkaline solution, in the proportion of 6 atoms I to 1 mol.phenol, For the analysis 2-3 grammes phenol are dissolved in sodium hydroxide solution (3 eq. NaHO to 1 eq. phenol) and made up to 500 C.C. with water; 10 C.C. of this are placed in a flask, warmed to 60° C., and decinormal iodine added until the solution is faintly yellow, with formation of a red precipitate. When cold, solution is acidified with dilute H2S04, made up to 500 C.C. and filtered. I n 100 C.C. of the filtrate, the excess of I is titrated with decinormal sodium thiosulphate ; this amount, deducted from the total I used, gives amount absorbed by phenol, which, when multiplied by 0*12351S, gives amount of phenol in sample assayed. W. J. S. The Estimation of Glycerine by t h e Benedikt-Zsigmondy Method.C. Mangold (2eitsch.f. angew. Chem., 1891, p. 400).-The reduction of the excess of permanganate by means of hydrogen peroxide, first proposed by Herbig, is recommended in preference to sodium sulphite, as used by Allen. The author simplifies the method by carrying out the oxidation in the cold, H0 operates as follows :--0*2 to 004 gramme of glycerine are dissolved in about 300 C.C. of water, 10 grammes potassium hydrate and so much 5 per cent. solution of permanganate is added, that for each part of glycerine about seven parts of permanganate are present. The mixture is allowed to stand at ordinary temperature for half an hour. Hydrogen peroxide is then added until the liquid is colourless, well shaken, filled up to one litre, 500 C.C. are filtered off through a dry filter, boiled for half an hour to destroy the excess of peroxide, allowed t o 80QC,, and after acidulation with dilute sulphuric acid, the oxalic acid standard permanganate. The author gives satisfactory test experiments. cool to about titrated with 0. H. On Coffee and Rice-Flour Adulteration, Ed. Maandbl Vervalsc h. May, lSSl.-The author lately examined a sample of coffee-berries, which the buyer BUS- pected to be an artificial product consisting chiefly of baked dough. There was, however, no mistake about their being genuine ccffee, although unusually strongly coloured. As, however, the microscopical examination showed a remarkable freedom from oily globules, the author thought it as well to make a chemical analysis, which clearly proved the berries had been thoroughly exhausted (no doubt to manufacture coffee extract), and afterwards stained. The same author also again calls attention to the adulteration of rice-flour with carbonate of calcium (marble) ; one sample containing no Iess than 56 per cent. of marble.

ISSN:0003-2654    

DOI:10.1039/AN8911600151

出版商:RSC    

年代:1891

数据来源: RSC

摘要:

I60 THE ANALYST. ERRATA.-In the June number, page 120, letter to Editor, for Nitrogen as nitrates, etc. Nitrites read Nitrogen as Nitrates and nitrites, in both places where it ocgurs,

ISSN:0003-2654    

DOI:10.1039/AN8911600160

出版商:RSC    

年代:1891

数据来源: RSC