摘要:

T.HE ANALYST. APRIL, 1896. NOT13 ON THE TITRATION OF QUININE. By ALFRED H. ALLEN. (Read at the Meeting, Pebrunry 5, 1896.) IN titrating alkaloids much depends on the indicator employed and the method of applying it. Methyl-orange, rosolic acid, iodeosin, phloxin, phenol-phthaleh, gallein, lacmoid, brazil-wood, logwood, litmus, and cochineal have all been employed and have found advocates. The behaviour of the alkaloids and organic bases with indicators of neutrality has been very imperfectly studied. I t is frequently stated that a certain alkaloid is distinctly alkaline (presumably to litmus), but it is only rarely and of recent years that chemists appear to have attempted to estimate alkaloids by titration with standard acid. Litmus answers in some cases, but by no means invariably.With methyl-orange, in the majority of cases a determination of tolerable accuracy and a fairly sharp end- Where this is desired, phenol-phthalein is quite inapplicable.86 THE ANALYST. reaction are obtainable. Cochineal, brazil-wood, and logwood are often useful indicators. In titrating quinine, an anomaly occurs which has misled more than one observer. This arises from the fact that the ordinary quinine sulphate of commerce, having, when anhydrous, the formula (C,,H,,N,O,),,H,SO,, though practically neutral to brizzil-wood, logwood, and cochineal, is strongly alkaline to methyl-orange. The point of neutrality when titrating qginine with cochineal, braxil-wood, or logwood, is therefore reached when sufficient acid has been added to convert the quinine into the sparingly soluble sulphate of the formula Qu,,H,SO, ; whereas in the case of methyl- orange the end-reaction corresponds to the formation of the readily soluble acid sulphate of the formula Qu,H,SO,.Hence twice the volume of standard acid will be required by a given weight of quinine when methyl-orange is employed, as when brazil-wood, logwood, or cochineal is used as the indicator. If nitric acid or hydro- chloric acid be substituted for sulphuric acid, the results are similar, the salts Qu,2HN03 and Qu,2HC1 being neutral to methyl-orange. The sparingly-soluble sulphate, Qu2,H2SO4, is distinctly alkaline to litmus, and hence this indicator cannot be conveniently used for the titration of quinine, though the end-reaction is well marked. The fact that Qu,H,SO, is neutral to brazil-wood, and QuH,SO, to niethyl- orange, is parallel to many other instances, the most interesting being that of the phosphates of sodium. Thus : NaH,PO, is neutral to methyl-orange.Na,HPO, is neutral to phenol-phthalein. Na,PO, is neutral to “ Poirrier’s blue, C.L.B.” The foregoing statements are a record of facts observed independently in my laboratory, and carefully verified by numerous experiments. The main fact, how- ever, was previously recorded by Seaton and Richmond (ANALYST, xv. 43), who state that they ‘‘ found that quinine bisulphate is neutral to methyl-orange, while the base itself has no action on phenol-phthalein,” and they based on these facts a process for the determination of quiuine in medicines. Their instructions assume that the medicine originally contained excess of acid, and was free from any inorganic base precipitable by baryta.Seaton and Richmond give figures showing that the method is fairly accurate when applied to pure sulphate of quinine, but the conditions under which the titrations are performed in practice render the method of little value. I t is useless in presence of citric and other organic acids, and the colouring matter present in quinine wine prevents the end of the reaction from being accurately observed. Owing to no formula for ‘‘ quinine bisulphate ” being given by Seaton and Rich- mond, nor the consequences pointed out, the fact on which their process was based was misinterpreted by me (‘‘ Commercial Organic Analysis,’’ vol. iii., part ii., p. 403, footnote), and apparently has been quite overlooked by other writers. Nxperiments made in my laboratory on the titration of cinchonine and ciuchoni- dine with various indicators had led to such anomalous results as to render it doubtful if the constitution of these bases, or at least the composition of the com- mercial article, is correctly understood.THE ANALYST. My thanks are due to Mr. A. B. Searle for the referred to in this note. DISCUSSION. The PRESIDENT said that Mr. Allen had stated The facts as to the titration of the quinine alkaloids. 87 execution of the experiments \‘erg clearly and concisely the parallel drawn between quinine compounds and phosphates was especially interesting. I t was easy to understand how readily errors might be made in quinine estimations, in consequence of the nomenclature of the quinine salts. A similar instance of ambiguity had occurred in the case of the two chlorides of mercury.

ISSN:0003-2654    

DOI:10.1039/AN896210085b

出版商:RSC    

年代:1896

数据来源: RSC

摘要:

THE ANALYST. 87 NOTE ON THE PREPARATION OF PURE HYDROFLUORIC ACID. By ALFHED H. ALLEN. ( R e a d at the Meeting, February 5, 1896.) COMMERCIAL hydrofluoric acid is liable to contain various impurities, including lead, iron, aluminium, calcium sulphate, organic matter, etc. I n the absence of a platinum still it is not easy to prepare a strong acid suitable for use in the analysis of silicates, but the necessity of obtaining a product free from fixed impurities led me, some years since, to adopt the following contrivance, which I have since used with very satis- factory results. The apparatus simply consists of the largest platinum crucible available. I n this is placed a mixture of ordinary hydrofluoric acid with about an equal measure of strong sulphuric acid. I n a smaller platinum crucible is placed a weighed quantity of the silicate to be treated, and this is moistened with three or four drops of strong sulphuric acid. The smaller crucible is then placed inside the larger, and is pre- ferably supported on a disc of plaster of Paris, or on a ring cut from a piece of one- inch leaden gas-pipe.The larger crucible is then covered with a platinum dish filled with cold water. On heating the arrangement on an iron plate, the hydrofluoric acid in the outer crucible is volatilized, and is condensed on the lower surface of the platinum dish, from which it drops on to the silicate contained in the inner crucible. After a time, when about 10 C.C. of distillate has collected in the inner crucible, the latter is removed, the contents evaporated off, and the treatment once or twice repeated, to ensure the complete decomposition of the silicate. By the foregoing means pure concentrated hydrofluoric acid is prepared at the time and in the exact quantity required, without the use of any special apparatus. I)ISCUSSION. Mr. BLOUNT said that he had distilled absolutely pure hydrofluoric acid in a leaden vessel, having an exit tube sloped upwards, and connected with a platinum condensing-tube sloped downwards, so that the condensed acid came into contact with platinum alone. This was a very convenient plan, as a fairly large quantity of the acid could be made at one operation. Mr. BLLZX said that when a small quantity of lead in the hydrofluoric acid was of no consequence, he had himself used a leaden retort constructed out of gas-pipe, but without the platinum tube mentioned by Mr. Blount.

ISSN:0003-2654    

DOI:10.1039/AN8962100087

出版商:RSC    

年代:1896

数据来源: RSC

摘要:

88 THE ANALYST. THE COMPOSITION OF MILK AND MILK PRODUCTS. By H. DROOP RICHMOND. (Read at the Meeting, February 5, 1896.) THIS paper gives a ~ e ' s z m k of the work done in the laboratory of the Aylesbury Dairy Company during the year 1895. Of the 30,068 samples analysed during 1895, 24,662 were milk samples, and the mean composition of 11,081 received from the farms is given in Table I. : .January ... March ... April . . . . . . May . . . . . . June . . . . . . July . . . . . . August . . September . , . October ... November ... December ... February ... Average ... A\.M. Milk. 1,0325 12-76 3-87 1-0326 12-72 3-81 1,0326 12.48 3.60 1.0324 12:48 3 65 1.0327 16-40 3-50 1-0323 12-21 3-43 1.0320 12-14 3-46 1.0318 12.18 3-49 1-0321 12.24 3.51 1-0326 12-67 3.77 1.0326 12.i.1 3.83 1.0327 12.63 3.71 1.0321 12-47 3-64 8-89 8'91 8.88 8.84 8'90 8.78 8'69 8-67 8.73 8-90 5-91 S-92 8-53 P.M.Milk. 1.0323 13-15 4'23 8-92 1-0324 13-16 4-23 8-93 1-0324 12-88 4.00 5.88 1.0322 12-86 4-03 8.83 1-0323 12-74 3.90 8-84 1-0;?19 12-49 3-78 8-71 1.0315 1251 3-57 8-64 1.0314 12-60 3-96 8-64 1-0316 1259 3'91 8-68 1.0321 13.15 4.3'2 8-85 1'0322 13-10 4'24 8.86 1.0324 12-97 4.03 8.89 1-0321 12-84 4.03 8.81 Mean. 1'0324 1.0325 1.0325 1.0323 1 m0325 1 -0321 1.0317 1.0316 1.0319 1 -0323 1-0324 1.03'36 1'0322 12.95 4-05 12-94 4-02 12.68 3-80 12.68 5.84 12-57 3TO 12-36 3.60 12.33 3-86 12.38 3-72 12.41 3-71 12-91 4-04 12-92 4.03 12-80 3.89 12.66 5.84 8.90 8'92 8-88 8-54 8.8; 8.i6 8 -67 8-66 8 -70 8-87 8.89 8-91 8-82 The results are given to show the difference between the morning and evening No cases of the fat falling below 3.0 per cent.in the mixed milk from any farm The mean composition of the milk of the goat and the ass is : milks. have been observed during the year. Goat. Ass. Total solids ... ... 13-24 10-23 Fat ... ... ... 3.78 1.18 Sugar ... ... ... 4.49 6-86 Proteids ... ... ... 4-10 1.74 Ash ... ... . . . . -87 -45 As the composition of cream produced by separators is wholly dependent on the adjustment of the separator, the average composition of cream has no scientific iniport, and the table which has been given in former years is omitted. The analysis of one sample of unusually thick cream, which was made for experimental purposes, was as follows : Total solids ... -.. ... 68-18 Fat ... ... ... ... 64-88 Ash ...... ... ... -28 Solids-not -f at ... ... ... 3-30 Ratio of 100 parts of water to solids-not-fat = 10.4. This cream was analysed to see whether the view put forward in a former paper (ANALYST, xix., 73), that the ratio of w-ater to solids-not-fat was the same in cream as in milk, and therefore that the fat did not carry any proteids, was borne out in cream of great thickness. Were it a fact that the fat did carry proteids, the ratio ofT E E ANALYST. 89 solids-not-fat to water should be distinctly higher in very rich cream than in milk. It was, however, found that the ratio was identical with that in the milk used for its preparation. The composition of clotted cream was as follows : Maximum. Mini mum. Average. Total solids ... ... 73-77 59-01 66.81 Fat ...... ... 66.89 48.27 58-21 Ash ... ... ... 1-17 -49 .71 Solids-not-fat ... ... 11.70 5-85 8-60 The ratio of the ash to solids-not-fat = 1 : 12 is the same in clotted cream as in milk. The bulk of the fat estimations in all products was made by the Leffmann-Beam method ; the Gerber method, in which the chemical principles of the Leflfmann-Beam method have been incorporated, has also been used, on account of the manner in which the machine employed lends itself to modification. Two centrifugal machines, one having a steam turbine fitted, and the other a water motor, have been employed with very satisfactory results as compared with hand-driving gear. The following Reichert figures have been found in butter during the year : Maximum. Minimum. Average. R.W. Figure.French butter ... 14-35 12.4 13.28 x 2.2 = 29.2 Irish butter ... 13-7 11.5 13-00 ,? 28.6 Australian butter 15.2 13.4 14.17 9 , 31.2 ... ... The percentage of water has been as follows : Maximum. Minimum. Average. French fresh butter ... 18.00 12-25 14.78 9 , salt Y 9 ... 14.43 10.25 12.97 Australian salt butter ... 15.72 9 -09 12.82 Irish butter ... ... 15.54 11.84 13-68 English fresh butter, I. ... 16.26 11-87 13.79 direct from churning, ,, salt ,, I. ... 18.06 11.77 14.74 direct froiii churning. 9 9 , I ,, rr. ... 15-71 12-50 13.54 24-48 hours old. ,, 11. ... 16.63 10.30 13.33 24-48 hours old. 2 , 7 , ,, IIT. ... 15.09 9.69 12.00 10-30 days old. 9 , , J The percentage of water was also calculated for the summer and winter months respectively : Summer. Winter.French fresh butter ... 14.46 per cent. 15.09 per cent. English butter.. . ... 14.17 ,, 13.33 ,, (all kinds). The following tables show the frequency with which amounts of water differing by 1 per cent. were found : FRENCH FRESH BUTTER. 18-19 1 -2 17-18 6 1-3 16-17 32 7.1 15-16 137 30.4 14-15 190 42.1 18-14 83 18.4 12--13 2 -4 Per Cent. Water. No, of Samples. Per Cent. on Total. Total 451 99.990 THE ANA4LYST. FRENCH SALT BUTTER. 14-15 7 14.6 13-14 23 47.9 12-13 9 18.8 11-12 7 14.6 10-11 2 4-2 Total 48 100.1 Per Cent. Water. No. of Samples. Per Cent. on Total. - -- The English fresh butters (all churned at Bayswater) were divided into two classes : I. Samples taken immediately after churning. 11. ,, ,, after a lapse ol 24 to 48 hours. 1. 11. Per Cent. of Water.No. of Samples. Per Cent, on Total. No, of Samples. Per Cenb. on Total. 16-17 1 1.7 15-16 6 10.3 2 10 14-15 18 31.3 3 15 13-14 19 32.8 7 35 12-13 12 20.7 8 40 11-12 2 3.4 - - Total 58 20 The English salt butters were similarly divided into three classes : Per Cent. of Water. 18-19 17-18 16-17 15-14 14-13 13-12 12-11 11-10 10-11 9-10 I. Samples taken immediately after churning. 11- 9 ) ,, after a lapse of 24-48 hours. 111. ,, 9 , J J , J 10-30 days. I. 11. 111. Samples. Total. Samples, Total. Samples. Total. No. of Per Cent. on No. of Per Cent. on No. of Per Cent. on 1 1.3 2 2.5 12 15.0 3 3-8 18 22-5 4 5.1 1 3.6 20 25.0 10 12.6 20 25.0 27 34.1 3 10.7 G 7.5 30 38.0 8 28-6 1 1-3 4 5.1 12 42.9 -. - 1 1.3 3 10.7 - - 1 3.6 - - -- Totals 80 79 28 I t was found by experiment that the loss of water from salt butter was practi- cally complete after the first week, and it is quite legitimate to average butters from 10 to 30 days old.The following conclusions are drawn : I. French butters, both fresh and salt, have contained fully 1 per cent. more water than in former years (see former reports). 11. From the experiments on English butters it is seen that fresh butter losesTHE ANALYST. 91 a very small amount of water on keeping; salt butter, on the contrary, loses water very rapidly, especially during the first day or two after making, and more slowly during the next week, when the loss nearly ceases. I t appears that the loss of water from fresh butter is due chiefly to evaporation, and the loss of water from salt butter chiefly to brine running out.I t is interesting to note in connection with this that duplicate analyses of fresh butter (taken from different parts of a lump) have never differed iiiore than 0-26 per cent., while differences of 0.7 per cent, have been observed with salt butter. 111. French fresh butter contains more water in winter than in summer ; English butters contain more water in summer than in winter. The number of English butters prepared in winter was, however, small (66), and of these only four were pre- pared during the winter proper (December to February) ; the average of these four was 14.27 per cent., or -1 per cent. higher than the summer average. I t seems that exceptionally high temperatures and exceptionally low temperatures have a, tendency to cause butter to contain a, high percentage of water.IV. Taking butter from 24 to 48 hours old to represent commercial butter, it is seen that fresh butter on the average contains more water than salt butter. I t appears from the tables above that when sampled directly after churning, salt butter contains more water than fresh; but this conclusion is not wholly justified. I t is known that certain conditions of the cream churned are favourable to a low percentage of water in butter, and the cream used for churning fresh butter fulfilled those conditions better than that used for churning salt butter. I n the few cases where both fresh and salt butter were made from the same cream, the amounts of water were nearly identical. There appears to be little foundation for the commonly accepted statement that salt butter contains more water than fresh butter, V.I t has been observed that, broadly speaking, the nearer the percentage of water is to 13.5, the better is the quality of the butter, and that when the limits of 12 per cent. on one hand, and 15 per cent. on the other are overstepped, there is, in a large number of cases, a niarked falling off in quality. This rule is, however, far from absolute. I t is kuown that water is added to butter as an adulterant, and there is no method of distinguishing between water fraudulently added to butter and that naturally found therein. One chemical method and two so-called c c practical ” methods have been put forward. The chemical method is based on the fact that butter contains a certain amount of solids-not-fat, which would be reduced by adding water; Vieth (ANALYST, xvi.1) was, I believe, the first to calculate the ratio of the solids-not-fat to 100 parts of water, and to point out that in unwashed butters there were 10 parts of solids-not-fat to 100 of water, while washed butters contained 5 parts ; he also pointed out that the variations were considerable. But for the fact that this method has been seriously recommended to public analysts by a butter dealer, hlr. Gibson (Iicyort Food Products Adzdteration, Blue Book, No. 3G3, 2078-2079), it would be hardly necessary to give quantitative results. I have taken a series of 109 samples of butter known to be without addition of92 THE ANALYST. water (including some insufficiently worked), and have calculated the proportion of solids-not-fat to 100 parts of water ; the results are contained in the following table : S.-n.-F. to 100 parts Water. 14 11-12 10-11 8-9 7-8 6-7 5-6 4-5 3-4 2-9 No. of Samples. 1 1 1 6 16 26 31 19 7 1 I I Percentage of Water. Max. Min. 13-64 11.30 14.97 10.19 14-64 11.08 15-33 10.36 19.23 11.01 14.74 11.90 Average. 10.28 13-48 12.87 12.61 12-82 12-87 12.94 14.06 13-41 I took 90 parts of a sample of butter which contained 12.5 per cent. water, and mixed 10 parts of water with it ; it gave the following figures on analysis : Water ... ... ... ... 21.06 per cent. Fat ... ..- ... ... ... 75.84 ,, ,, Salt ... ... ... ... ... 2.46 ,, ,, Solids-not-fat ... ... ... ... -64 ,, ,, Ratio of solids-not-fat to 100 of water ... 3-0 ,, ,, Though I believe any public analyst would have condemned this sample, solely on account of the amount of water present, the ratio of solids-not-fat to 100 parts of water does not fall below the minimum found in genuine butters, and it would have to be passed by the proposed test. I need not further comment on the method.

ISSN:0003-2654    

DOI:10.1039/AN8962100088

出版商:RSC    

年代:1896

数据来源: RSC

摘要:

92 THE ANALYST. FURTHER NOTES ON THE DETECTION OF FORMALIN. BY H. DROOP RICHMOND AND 1,. K. BOSELEY. (Read at the Ncetiizg, Jfarcl/ 4, 1896.) IN a former paper on this subject (ANALYST, xx. 154) an error has crept into the text with regard to the number of molecules of ammonia which react with formaldehyde. Legler states that 4 molecules of ammonia react with 6 of formaldehyde, and Losekan maintains that 6 molecules are equal to 6 of formaldehyde. In the same number of the h A L Y S T (p. 157) Rideal states that the formalin used for milk preservation contains 2 ounces of formaldehyde to the gallon, or 1 : 320. This ratio is an error, the true ratio being 1 : 80 (or 2 : 160). He states also that + pint of this solution is added to the churn of seventeen to eighteen gallons, ie., 1 part diluted formalin to 288 parts milk.From these data he concludes that 1 part of formaldehyde is contained in 46080 parts of milk, and a retro-calculation shows that he has neither used the correct ratio of 2 ounces to the gallon = 1 : 80, nor his assumed ratio 1 : 320, but a ratio of 1 : 160. Rideal also states that all milks give a pink colour when mixed with SchiPs reagent, and concludes that milk contains a non-volatile aldehydic compound. HeTHE ANALYST. has, however, completely overlooked the fact that aldehydes do not give a pink colour with Schiff‘s reagent, but a reddish violet one ; while alkalies, either free or combined with a weak acid, give a pink colour. We find that in the presence of an acid, even when very dilute, the pink colour is not developed in milk, while the inhibitory effect of dilute acid on the colour given by aldehydes is negligeable.Indeed, if Schiff’s reagent is prepared according to Caro’s directions with rosaniline, sodium sulphite, and hydrochloric acid, it always contains an excess of hydrochloric acid. On p. 167 of the same journal an abstract of a paper by Weigle and Merkel is given. L4s a proof that formalin has an adverse influence on peptic digestion, they adduce the fact that an addition of formalin to milk renders the casein insoluble in pepsin and hydrochloric acid. As without the addition o€ formalin the insoluble casein-dys-peptone is formed, it is difficult to see that their observation proves that formalin renders the albuminoids of milk less digestible.We have studied the comparative delicacy of the reactions employed for detecting formalin. Of the general aldehyde reactions, we find that the reduction of silver nitrate is, though very delicate, of so general a character as to be misleading, even when following Tollen’s directions to test in the cold with a mixture of 3 grammes silver nitrate dissolved in 30 C.C. of ammonia (specific gravity .923), and 3 grammes sodium hydroxide in 30 of water (BcT., xv. 1635). Schiff’s test is also very delicate, but must be performed in a slightly acid solution. We do not find that milk-sugar, even after boiling with dilute sulphuric acid, gives any colour, and consider that it is quite safe to test the whey produced by adding dilute sulphuric acid to milk, especially as the test, not being characteristic, is only of a preliminary kind.We have not thought it necessary to investigate the delicacy of the para-diazo- benzene-sulphonic acid test, the resorcinol test, nor the nitro-prusside test. We find that the delicacy of Hehner’s reaction may be much increased by diluting the milk with an equal bulk of water and adding sulphuric acid of 90 to 94 per cent. strength. Under these conditions milk, in the absence of formaldehyde, gives a slight greenish tinge at the junction of the two liquids, while a violet ring is formed when formaldehyde is present. I n the absence of fornialdehydc a brownish-red colour is developed after some hours, not at the junction of the two liquids, but lower down in the acid. I t cannot be mistaken by anyone who has had any experience with the test for the formaldehyde reaction.By using this modified test, the use of milk is more convenient than that of peptone when testing in aqueous solution (e.g., a distillate). The delicacy of Hehner’s test is about equal to that of Schiff‘s. Trillat’s reaction with dimethylaniline is less delicate, but does not require any distillation, The lead oxide mentioned in 3ur former note should be lead peroxide (PbO,). The troublesome distillation is avoided in this way. This colour is permanent for two or three days. The blue colour is not very stable. Plochl’s test fails with very small amounts of formaldehyde. We find that our test with diphenylamine is not of very great delicacy. ThGugh we had no difficulty in getting a reaction with milk to which the amount of formalin solution prescribed by the vendors was added, we find that Hehner’s and Schiffs tests give distinct reactions when ours fails.The statement that the precipitate is94 THE ANALYST. coloured green if the acid used contained nitrates is incorrect. We find that when acid free from nitrates is used, the green coloration still appears on continued boiling. Of about equal delicacy is Trillat’s aniline test. I t is necessary to operate in the cold, as the precipitats is easily soluble in hot water, being again deposited on cooling. The precipitate given by acetaldehyde with aniline is very much more soluble than that given by formaldehyde. By boiling a solution of hydrazine sulphate, t o which a slight excess of caustic soda solution has been added, with formaldehyde, formalazine is produced as a yellowish-white flocculent precipitate. This reaction is of less delicacy than any of the foregoing. We have attempted the preparation of thio-meta-formaldehyde as a test for formalin, but without success in dilute solutions, though Wohl states that it is in- soluble. We prefer t o rely on Hehner’s test (xith the modification mentioned above) for the detection of formalin in milk, and to use Schiffs test (in the whey produced by sulphuric acid) and Trillat’s dimethylaniline test to confirm, and if the quantity appears large from the above reactions, to distil the milk into diphenylamine dis- solved in a slight excess of sulphuric acid, and boil.

ISSN:0003-2654    

DOI:10.1039/AN8962100092

出版商:RSC    

年代:1896

数据来源: RSC

摘要:

94 THE ANALYST. THE DETECTION OF FORMALIN. BY OTTO HEHNER. (Read at the Meeting, March 4, 1896.) SCHIFF’S reagent as a test for foriiialdehyde is far froni satisfactory. Apart fro111 the fact that it reacts with all aldehydes, and is, therefore, not applicable to fermented beverages or fluids, such as wine or vinegar, which contain naturally traces of acetal- dehyde, or to food-substances which by fermentation might yield traces of acetal- dehyde, it acts but very slowly when very small quantities of formaldehyde have to be looked for, such as would be present in milk when preserved with fornialin in accordance with the instructions furnished by the vendors. If these instructions are complied with, about one part of formaldehyde only is present in about sixty thousand parts of milk.Schiff’s reagent is quite capable of indicating such traces, but only after some hours, or when the distillate froiii the milk plus Schiff‘s reagent has stood over night, As pointed out by Richmond and Boseley in their recent paper (ANALYST, xx. 154), when an excess of sulphurous acid is used in the preparation of the reagent, no reaction is obtained with traces of formaldehyde, while ‘ I the red colora- tion appears on warming Schiffs reagent, on blowing air through it, or even on placing it in an uncorked bottle.” I can fully confirin these statements, and can further add that Schiffs reagent may give a red coloration on standing for a short time eren with pure distilled water in stoppered cylinders, or with a distillate from milk wbich is perfectly free from formalin.Thus, if to 25 C.C. of wattr only one or two drops of Schiff‘s reagent are added, a red colour appears already in half an hour,THE ANALYST. 95 the amount of oxygen contained in the water being sufficient to oxidize the sulphurous acid contained in the added reagent, even though the mixture has been placed in a stoppered cylinder filled to the neck. When a little more Schiffs reagent is added -say ten drops-the coloration does not appear. It follows that an analyst who is not aware of this circumstance-and so far attention has not been drawn to it-may in one of two samples of milk, both equally free froin formalin, apparently find formalin in the one and not in the other, although he may have apparently operated under precisely the same conditions in both.I find that the best way of operating is to add about five drops of the reagent to the distillate from 100 C.C. of milk (amounting to about 25 c.c.), place the mixture in a stoppered cylinder, to observe the colour next morning, and then to add a few drops of sulphurous acid solution. After a short time any colour which may be due to oxidation will have vanished, while that due to the presence of an aldehyde remains. There is certainly a difference in the tint produced by colour oxidation, which resembles that of rosaniline, and that of the aldehyde compound, which is violet ; and with those small traces with which we have often to deal, only a comparison of the relative colours would allow of anything like a safe conclusion being drawn. From the experience I have collected I am clearly of opinion that Schiff's test is a dangerous one, and should only be used as a confirmation.I have made some experiments as to the rate at which formalin disappears froin milk on keeping. To three portions of pure inilk formaldehyde was added in the proportions of 1 of the aldehyde to 25,000, 1 to 50,000, and 1 to 100,000, the milk thus preserved being kept in stoppered bottles. After one week no foriiialin could be detected in the sample containing 1 part in 100,000; after two weeks none in the 1 in 50,000 sample ; while after three weeks there was only the faintest trace discover- able in the 1 in 25,000 sample. These experiments were made in .January, when the temperature was low, the Schiffs reagent being used with the precautions described. The reaction which Messrs.Richmond and Boseley have described in the paper alluded to (loc. cit.j as having been first pointed out to them by myself, and which depends upon the blue colour produced when mill< containing formaldehyde is mixed with sulphuric acid, is infinitely more characteristic than Schiff's re- action, especially when the test is applied in the form given it by Mr. Richmond, where the milk to be tested is allowed to float upon the surface of sulphuric acid, anhydrous, or nearly so, contained in a test-tube. I find that in this way one part of formaldehyde can be readily detected in 200,000 parts of milk. Acetaldehyde does not give this reaction, and as no distillation is required, the test is of the simplest possible nature as regards milk.I cannot bear out the statement of Messrs. Richmond and Boseley that it is possible to obtain a blue coloration with formaldehyde to which some peptone solution had been added. The peptones which I used, and which undoubtedly were rich in peptone, gave no blue coloration. Egg-albumen does give the reaction in the presence of formalin, but so feebly as to lead me to conclude that it is not the albumen itself, but some trace of impurity contained in it, which enters into the reaction. Casein precipitated from milk, re-dissolved in alkali, and again precipitated and dissolved, gives the colour most strongly. Milk-whey also gives it, but gelatin, as already pointed out by Richmond and Boseley, does not. I have tried96 THE ANALYST.many other substances likely to be present in milk, but have found nothing so satis- factory as casein. To test wine or vinegar for formaldehyde, I add a drop of milk to the sample, and pour the mixture carefully on the surface of strong sulphuric acid contained in a test-tube. A blue ring appears at the zone of contact when formalin is present, while ordinary aldehyde gives no reaction. The test is also well fitted for the detection of formaldehyde in butter, the aqueous liquor resulting when the butter is melted for analysis being used. The following is another equally sensitive and characteristic test, If to the distillate from a sample of milk, etc., one drop of a dilute aqueous solution of phenol is added, and the mixture poured upon strong sulphuric acid contained in a test-tube, a bright crimson colour appears iii the zone of contact.This colour is still readily seen with one part of formaldehyde in 200,000 of water. If there is more than one part in 100,000, there is seen above the red ring a white, milky zone, while in stronger solutions a copious white or slightly pink, curdy precipitate is obtained. This reaction has the advantage of the one above referred to, inasmuch as it is obtained with formaldehyde solutions of all strengths, while the blue colour with milk is not obtained with milk containing much formaldehyde. I have not ascertained the upper liinit of sensitiveness of the reaction, but the blue colour is only obtained with traces. Acetaldehyde also gives a coloration and a precipitate with phenol and sulphuric acid, but it is orange-yellow, not crimson. Many other hydroxy-derivates of benzol, such as salicylic acid, resorcinol, and pyrogallol, give the red colour with formaldehyde.Hydroquinone does not give the red colour, only an orange-yellow one. The reaction only succeeds when carried out as described above; the phenol must first be mixed with the solution to be tested and the mixture poured upon the sulphuric acid. If the hydroxy-compound is first dissolved in the acid, and the formaldehyde solution then added, no colour is obtained. Of course it is very well known that formaldehyde most readily causes the con- densation of aromatic substances. T ~ u B , the tannins readily condense in the presence of hydrochloric acid, forming insoluble compounds. Richmond refers to Kleeberg (‘I Annalen,” 263, 253), who found that formaldehyde combines with phenols in the presence of hydrochloric acid, and Emil Nickel (Zeit.f. anal. Chew,., 1889, p. 5349) states that the phenols are useful reagents for aldehydes, and %ice versci, but as far as I am aware, the appearance of the red coloration with formaldehyde has not been previously noticed. The precipitate obtained by sulphuric acid, formaldehyde, and phenol is so insoluble that it might well be utilized for the determination of the strength of dilute formalin solutions. When a trace of the precipitate is taken, a few drops of bromine water or iodine solution added, and then a little sodiuni hydrate solution, a strong violet-red coloration and a precipitate are obtained. The silver reaction for aldehydes altogether fails with the faint traces of formalin which are readily recognisable with the milk-sulphuric and the phenol-sulphuric tests.Only a trace of phenol must be used.THE ANALYST. 97 Moreover, all distillates from pure milk show a very faint browning with ammoniacal silver solution. The diphenyl reaction referred to by Messrs. Richmond and Boseley is far less sensitive than the two reactions described in this paper. DISCUSSION. The PRESIDENT said that most of the tests hitherto employed for the detection of formaldehyde had been of such a character as to be applicable only to aldehydes as a class. The reaction shown by Mr. Hehner was, however, a very characteristic one, and likely to prove extremely useful. He had found that an aqueous solution of milk sugar gave a reaction with Schiffs reagent, and therefore distillation was necessary, Dr.RIDEAL remarked that allusion had been made to a paper published by hirn- self on the subject of formalin, but he thought that was hardly the right way to put it. I t would be remembered that in the course of the previous year Mr. Bevan had promised a paper on the use of formalin for preserving milk samples, which he was unable to bring forward on the date for which it was announced. EIe (Ur. Rideal) happened to be present at the meeting on that date, and had ventured to make a few remarks regarding formalin aud its detection, which the President suggested should be published, in the form of a note, in the ANALYST. Seeing that he had not attended the meeting with the intention of reading a paper, the appear- ance of the note in question was only due to the kindness of the meeting and the suggestion of the President ; but, in the event of any question arising as to the use of Schiff's test in connection with formalin, it was rather unfortunate thst this short note should have been placed after the papers of Mr.Bevan and Messrs. Richmond and Boseley, inasmuch as it was read at a previous meeting to that at which those papers were presented. With regard to hlr. Richmond's modification of Schiff's test, it was necessary to remember that formaldehyde was the only volatile aldehyde which had to be looked for, and that the original method of applying Schiff's reagent to the distillate tested was not merely for the detection of the presence of an aldehyde, but for that of a volatile aldehyde. I t seemed, therefore, to be preferable to adhere to the method suggested by himself, rather than to follow one which involved the application of the reagent to the original milk without distillation.The colour-test mentioned by Mr. Hehner seemed to be especially useful, for the reason that it was manifested when the sulphuric acid was added to the milk in sorting samples by the machine. Nr. WHITE observed that in the case of tnilk containing formalin, the clot formed on the addition of hydrochloric acid to the milk was much more difficult to dissolve than when no formalin had been added. Mr. W. NORTHFIELD YARROW remarked that the clot referred to by M i . White also took a yellowish tinge, if much formalin were present, while it remained whitish if there was none.Nr. C. A. MITHELL mentioned two tests which he had found useful for detectingTHE ANALYST. formaldehyde. One was the reduction of chromates by aldehydes, and the subsequent formation of a violet modification of the chromic salt. L4 mixture of 1 C.C. of nitric acid and an equal quantity of potassium chromate solution added to the distillate from the liquid under examination, produced, after a shorter or longer tirne, according to the quantity of the aldehyde present, a violet coloration. The other test was dependeut upon the action of formaldehyde on Nessler’s solution. A very small trace of formaldehyde was sufficient to produce a yellow colour, which gradually darkened and produced a precipitate at first resembling ferric oxide, but finally becoming dark gray.Dr. RIDEAL remarked that the test of smell, which had not been iiientioned either by Mr. Richrnoud or by Mr. Hehner, was very useful in detecting the presence of formalin. In milk, 1 part of formaldehyde in 25,000 could easily be recognised by its odour on warming the inilk. In the process of distillation, preliminary to the application of Schiff’s test, the first portions of the distillate possessed a pronounced odour of formalin. Mr. RICHJIOXD said that the fact of the non-occurrence of the blue reaction lrith sulphuric acid when formaldehyde was present in large quantity was mentioned in the paper by himself and Mr. Boseley (,~NALYST, xx. 155), and the insolubility of the caseiu reiferred to by 111..White had heen noticed by Mr. Seyler. The President had said that, under some conditions, milk sugar gave a reaction with Schiff’s test, but he (Ah. Richmond) had never been able to observe such a reaction, and would like to hear under what conditions it was obtained. As far as he (Mr. Richmond) and his colleague were concerned, they freely admitted the justice of Dr. Rideal’s claim ; in fact, so far from making any claim for its use, they were the first to point out its unreliability. With regard to llr. Rideal’s reniarks as to the modification of Schiff’s test which they had suggested, he would like to point out that acetaldehyde was volatile as well as formaldehyde, and that its antiseptic properties (although inferior to those of formaldehyde), were sufficient to admit of its use as a milk preservative. Mr. HEHKEN said it seemed to him ridiculous to talk of priority at all in con- nection with Schiff‘s test. Long before formaldehyde came into use as a preserva- tive, it was known that it gave a reaction with Schiffs reagent. With regard to the test of smell, no doubt the nose was a very useful organ, but it required backing up by something inore definite. Such a test was not, as a rule, accepted by chemists ; in legal cases especially something in addition was required which was discernible to the eye. The PRESIDENT said it was very difficult to define the conditions under which Schiff‘s test did or did not succeed, and therefore, although he had observed the coloration with milk sugar, he could not exactly lay down the conditions under which it would appear. Ordinary aldehyde did not give this reaction. Dr. Rideal had claimed priority with regard to the use of Schiff’s test. I t might be due to a sillall quantity of alkali.

ISSN:0003-2654    

DOI:10.1039/AN8962100094

出版商:RSC    

年代:1896

数据来源: RSC

摘要:

THE ANALYST. 99 OFFICIAL METHODS FOR THE ANALYSIS OF FERTILIZERS, ISSUED BY THE GERMAN MANURE MANUFACTURERS' ASSOCIATION, HARZBURG, MAY 28, 1895. CONTlCII<I'TI<D HT H. H. B. SHEPHNRD, ANGLO-CONTINENTAL GUANO WOI~KS, LONDON. I. DETERMINATION OF WATER. FOB the determination of moisture in superphosphates, saw phosphates, sulphate of ammonia, saltpetre, bone-ineal, dried blood, horn-powder, and similar substances, 10 graiiiiiies to be dried at 100" C. until a constant weight is obtained; substances containing gypsuni to be dried for three hours, Should any volatile matter, such as volatile amiiioniacnl salts, be present, it 'is to be separately determined, and the amount deducted froin the loss first Obtained. I I. 1) E: T 13: 11 3 I I Xi\ T I 0 N 0 1" I K S 0 L U H LE MATTE 13.The determination of the insoluble matter, like that of the moisture, is required principally for such purposes as calculating results into the pure or dried state. I t is to be carried out as follows : Ten grarnnies to be taken, and ( u ) if the solution is niade in acid, to be evaporated to dryness, to render the silica insoluble, and the residue filtered ofY, washed, and ignited. ( b ) If the solution is made in water, the residue to be filtered off, washed, and dried at 100" C. until the weight remains constant. 111. DETl~~E3IINATIOK OF PHOSPHOItIC ACID. A. I;cti~ospcct.-Owing to differences frequently occurring between the results obtained by works' cheinists and the clieinists of the experimental stations, it was thoaght desirable in the year 1889 to institute an inquiry into the matter.A meeting of the cheiiiists of the German experimental stations was held at Bremen in 1890, in conjunction with representatives of the German Manure Nanufacturers' Association, and it was decided to send uniformly inised samples of various superphosphates to different experimental stations and works' laboratories for the purpose of comparing the molybdate and citrate methods for determination of phosphoric acid, and of testing the various processes in use for the extraction of soluble phosphate. This plan was duly carried out ; but the results, especially those obtained by the inolylsdate method, were not considered satisfactory, and it was decided at the next meeting, held at Halle in 1891, to pursue the inquiry further.I t was desired, in the first place, to make a study of the rnolybdate method, by employing a solution of phosphoric acid of known strength, with the view of issuing reliable working in- structions for this method, and at the same time to investigate the alternative citrate method. As regards the method of extraction, a complete agreement had already been arrived at. These further experiments mere carried out siiiiultaneously in May, 1892, by the chemists of thirteen experinientaJ stations and five works. The results by the molybdate method were again discordant ; but the citrate iiiethod gave sufficiently good results , even though the ammonium magnesium phosphate precipitate contained100 THE ANALYST. some calcium phosphate. I t was, therefore, decided to accept this method for the determination of the soluble phosphoric acid in superphosphates.The cause of the differences in the results obtained by the use of the molybdate method was the subject of discussion at the fifth general meeting of the chemists of the experimental stations, held at Berlin in 1892, in which representatives chosen by the German Manure Manufacturers’ Association took part, and was traced to differences in procedure between the different chemists. I t was then thought tha,t concordant results might be obtained by issuing exact directions for working the method, and by operating upon a solution of phosphoric acid of known strength and of a composition similar to a solution of superphosphate. I t transpired in the course of the discussion that three principal modifications of the molybdate method were followed-vix., that in use at the laboratory at Halle, that of Fresenius, arid that of Professor Wagner of Darmstadt. Detailed descriptions of these three processes were accordingly prepared and sent to the members, and in the spring of 1893 they were tried at five works and twenty-nine experipiental stations, the results being published at the sixth general meeting held at Wiirzburg in the autumn of the same year.The results, however, were again disappointing, and it seemed that the more accurately the details were carried out, the greater were the divergencies experienced. I t was, nevertheless, resolved to follow up the experience already gained by making still further experi- ments, and especially to give attention to the researches of Neubauer on the subject..-\s was made known through the medium of the official report of the Dresden meeting of September, 1894,* this resolution was acted upon by the chemists of the experimental stations, but without the co-operation of the committee of the Manure Manufacturers’ Association. A solution of absolutely pure potassium phosphate was prepared by neutralizing pure potassium carbonate with phosphoric acid obtained by the coiiibustion of pure phosphorus, and with this solution fresh experiments were made both with the niolybdate and the citrate methods. No conditions, however, were laid down for working the niolybdate method, it being left to each cheinist to use any recognised mode of procedure according to his judgment.The results obtained were most satisfactory, as, indeed, would be expected when dealing with a cheinically pure substance. Operating upon 0.150 graniine phosphoric acid for each experiment, nineteen out of twenty-three of the niolybdate determinations came within 0.001 grainiiie, corresponding to -1 per cent. in a superphosphate containing 15 per cent. phosphoric acid. The determinations by the citrate method showed also a remarkable agreement, the results of ten chemists not deviating more than 0.001 to 0.002 grarnme from the mean. As a consequence, it was decided to recommend that official analyses should continue to be carried out by some approved niodification of the rnolybdate method. The matter, therefore, stands at present thus, that for ordinary superphosphate testing the citrate method may be used, but for official analyses the molybdate method is to be employed.As, however, complete agreement on matters of detail was not arrived at, it was left to each chemist to adopt such plan as according to his judgment afforded the most accurate result. The analytical commission of the * La~dwi~khticli Versuc?&sstat., xlv., 350.THE ANALYST. 101 German Manure Manufacturers’ Association, on the strength of the experience obtained during the foregoing investigation, reconirnends the so-called Halle method, a description of which follows, as the one which furnished, comparatively speaking, the most concordant results. B. diznlysis of Swperphosphatcs and lZnzo Xatcrinls. -- Agreement has been arrived at upon all points here referred to.1. Prepnrutioib of tlzc Sa?i~pZes.*-(a) Dry samples of phosphates or other artificial fertilizers may be sifted and then mixed. ( b ) In the case of daiiip materials, where this is not possible, the preparation is to be confined to a careful mixing by hand. (c) In raw phosphates and animal charcoal, for reasons before mentioned, the moisture is first to be determined. ( d ) In Zealing with substances which lose water in the process of reducing to powder, the moisture is to be deterniined in the coarse aswell as in the fine, and the results of the analysis calculated into the original state as received. 2. Extyaction of Sii~~ci~lLosi)Ii(~tc.-The extraction of superphosphate is to be carried out as follows : Twenty graiiiiiies superphosphate to be introduced into a litre flask with SO0 C.C.water and shaken continuously for half an hour, then made up to the iiiark with water, mixed, and filtered. The filtration is ho be taken in hand promptly, as if left long standing, phosphoric acid separates out. They can be worked either by hand or by motor, and should make about 150 revolutions per minute. Solutions of concentrated superphosphate (so-called double superphosphate j should be boiled with nitric acid before precipitating the phosphoric acid, to convert any pyrophosphoric acid present into orthophosphoric acid. Ten C.C. of nitric acid of 1.4 spocific gravihy are sufficient for 25 C.C. solution. Vor ordinary work the citrate method may be used, but for official analyses the inolybdate method is to be employed. For the determination of the phosphoric acid in bone-meal, fish guano, meat- meal and raw phosphates,+ and the total phosphoric acid in superphosphates, 5 grarnmes are to be dissolved in 50 C.C. nitrohydrochloric acid, consisting of 3 parts hydrochloric acid of 1.2 specific gravity, and 1 part nitric acid of 1.25 specific gravity ; or the substance may be boiled for half an hour in a mixture of 20 C.C. nitric acid of 1.42 specific gravity and 50 C.C. sulphuric acid of 1.8 specific gravity. After cooling, the solution is to be made up to 250 C.C. For carrying out the shaking operation, shaking machines are desirable. (To he continued.) * I n accordance with the resolution of the third general meeting of the chemists of the experimental stations held at Bremen in 1890. Thornas-meal is referred to in another section.

ISSN:0003-2654    

DOI:10.1039/AN8962100099

出版商:RSC    

年代:1896

数据来源: RSC

摘要:

102 THE ANALYST. ORGANIC ANALYSIS. Reactions of Formaldehyde. Romijn. (Nedei*l. Tijdsclw. COOT Pka.mz. ClLem. C ~ L Toz. jiiiiz, 1895 ; through licr. Intc?*. des FaZsq., ix., pp. 13, 14.)-The author converts forinaldehyde into hexamethylene-tetramine by ammonia. This body forms regular crystals, and gives well-defined reactions. The substance under examination is distilled with water, and a drop of the distillate mixed on a microscope-slide with a drop of aminonia ; after evaporation the crystalline residue is examined, and tested with the following reagents : 1. Mercuric Chloride i i ~ excess.-Formation of crystals ; hexahedral at once, octahedral after a time. The latter are easily obtained from a solution containing 1 : 10,000, and are still visible in 1 : 100,000.THE ANALYST.1.03 2. Platinic Chloride.-Octahedral crystals, perceptible in 1 : 1,000, but not in 3. Phosphomolybdic Acid.-Rhomboidal crystals from solutions of 1 : 10,000. 4. Potassium Iodide 01' .Bimuth Iodide i n Potussizun Iodide.--In slightly acid solutions yellow crystals are formed, which are plainly seen in solutions containing 1 : 1,000, also in 1 : 10,000 after a time. 5. Hydrochloric Acid Solutiou ?f Stannous Chloi.icZe.-Needle-like crystals from a solution containing 1 : 1,000. 6. Nei-curic Iodide in Potnssizm Iodide, sliyl~dly cLcidi$ed ~ v i t l ~ Hyd~oclilo~ic Acid. -Bright yellow hexagonal crystals from solutions containing 1 : 10,000. 7. Iodim iiz Potc~ssiz~?n Iodide.-Rhoin bic crystals easily seen in solutions of 1 : 1,000. 8. Picric Acid-Crystals from a solution of 1 : 1,000.Many other bodies, as silver nitrate, mercurous nitrate, gold chloride, glacial acetic acid, etc., also give crystalline bodies, but the reaction with mercuric chloride 1 : 10,000. is chiefly relied upon. TV. P. s. A New Method of analysing Alkaline Benzoates. G. Rebikre. (Jozwn. Phu~m. et Chim., 1896, 113-116.)--This is based on the fact that iiiost mineral acids liberate benzoic acid from its metallic compounds. A small quantity, 11, of the benzoate is treated with a sufficient quantity of hydrochloric acid, and the mixture evaporated to dryness. The benxoic acid and the excess of hydrochloric acid are volatilized, and the metal is left as chloride. The amount of chlorine is then deter- mined with decinormal silver nitrate solution, To determine the benzoic acid, the same weight 1) of the benzoate is dissolved in 50 to 60 C.C.of water, and n C.C. of decinormal sulphuric acid added. This exactly saturates the base, and the liberated benzoic acid is titrated with decinormal soda, phenol-phthalein being used as indicator. This method can be used with most metallic benzoates, but in the case of lithium benzoate care must be taken to add the smallest possible excess of hydrochloric acid, and to evaporate on the water-bath in order to avoid loss by volatilization. In the case of ammonium benzoate the process is modified as follows : A given weight, p (about 0-20 gramme), of the benzoate is dissolved in 20 C.C. of decinormal soda, and the mixture boiled until all ammonia is expelled. The excess of alkali is then determined with decinormal acid (72 c.c.).The ainount of ammonium will be (20 - n) x 0.0018. I t is necessary to prove that the benzoate itself does not contain free acid. For the estimation of the benzoic acid, the same weight, p , of ammonium benzoate is dissolved in 20 C.C. of water, and (20 - i z ) C.C. of decinormal sulphuric or hydrochloric acid added. C.C. being taken. The liberated acid is then titrated with decinormal soda. C. A. M. The Biuret Reaction. Hugo Schiff. (Bcrl. Bey., xxix., 298.)-It is shown that not only biuret and albuminous substances give a red coloration with cupric sulphatc and caustic soda, but all bodies which contain two CONI3, groups, corn-104 THE ANALYST. bined in the molecule with a single carbon or nitrogen atom, or joined by one or more CONH groups.Oxamide also gives the reaction. 0. H. A Method of Estimating Uric Acid. E. Riegler. (Zeit. anal. Chem., 1896, 31-34.)-This method is based on the property of uric acid of reducing Fehling's solution. On the assumption that one molecule of uric acid reduces two molecules of copper sulphate, one gramme of uric acid should correspond to 0.7556 gramme of copper. In the actual determinations made by the author using pure uric acid the ratio was higher than this, one gramme of uric acid giving 0.5000 grainme of copper as the inean of ten determinations. For the determination of uric acid in urine, it is necessary to first separate it in a form in which it can be used with Fehling's solution. This may be effected by the method of Ludwig-Salkowski (Zeit. m2nZ.Chcm., xxiv., 637) or more rapidly by that of Fokker (ihit7., xiv. 206). Two hundred C.C. of urine are mixed with 10 C.C. of a saturated solution of sodium carbonate, allowed to stand for half an hour, and filtered from the precipitated phosphates. The precipitate is washed with 50 C.C. of hot water, and to the filtrate and wash-water 20 C.C. of a saturated solution of animoniuin chloride added. The liquid is well stirred, and after five hours filtered, preferably through a Schleicher and Schiill filter, No. 597, 11 cm. The precipitate is washed with 50 C.C. of water, and then introduced by means of a jet from a washing-bottle into a 300 C.C. beaker. Several drops of potash are added to clear the liquid, then 60 C.C. of Fehling's solution, and the whole well stirred.The beaker is then heated on a wire gauze until the liquid boils, the boiling being continued for five minutes. When the precipitate has subsided, the liquid is filtered through a sinall tough filter (Schleicher and Schiill, No. 590, 9 cni.), the precipitate well washed, and dissolved in 30 C.C. of nitric acid (specific gravity, I-l), the filter being washed with 60 C.C. of water. To this solution dry powdered sodium carbonate is added little by little until there is a permanent tnrbidity. The liquid is then cleared by the cautious addition of sulphuric acid, and made up to 100 C.C. Twenty-five C.C. of this are placed in a 100 C.C. flask, one grainme of potassium iodide in 10 C.C. of water added, allowed to stand for ten minutes, and titrated with thiosulphate solution (1 C.C.= 0.002 gramme uric acid), using starch as the indicator. To the total amount of uric acid found in the 200 C.C. of urine, an additional 0.030 gramme should be added to allow for the solubility of the ammonium urate in urine. Thiosulphate solution of the right strength is readily obtained by diluting 126 C.C. of a decinormal solution to 500 C.C. The reaction employed is : 2Cu(NO3), + 4KI = CU$, + 4KN0, + I,. The reduced cuprous oxide may also be weighed directly or reduced to metallic copper, as in the estimation of sugar. I n the latter case the ainount of copper, multiplied by the factor ___ 'Oo0 = 1.25, gives the corresponding amount of uric acid. c. A. R!. 0.8000THE ANALYST. 105 Detection of Vegetable and Animal Oils in Mineral Oils.C. Halphen. ( A m . CJzim. Analyt., 1896, 29.)-The author finds that the reaction proposed for this purpose by De la RoyBre, and which consists of adding to a few drops of the sus- pected oil, contained in a porcelain dish, two drops of a solution of fuchsine just decolorized with alkali, is valueless. Many carefully prepared mineral oils have an acid reaction, and restore the colour of the fiichsine solution. Soaps are often added to mineral lubricating oils, and in such cases the free acid of any added vegetable oil is neutralized, and consequently they do not respond to the above test. The presence of soap in such oils may readily be detected by their action on a solution of Congo-red which has just been rendered violet by hydrochloric acid.Soaps, notwithstanding their alkaline reaction, change the colour of this indicator to red. (?) W. J. S. On the Determination of the Degree of Oxidation of Oils. W. Bishop. (Jount. Phnrm. ct CIiint., 1896, 55-61.)-The process of Livache, which consists i l l determining the increase of weight in oils when exposed to the action of oxygen in contact with finely-divided lead, is only serviceable in the case of linseed-oil. I n other oils the oxidation proceeds too slowly. In order to obtain the most rapid oxidation, the main essential is to have the oil in as finely-divided state as possible by means of a porous neutral substance. The author found precipitated silica a suitable Sdividing agent, but the absorption was still too slow for practical purposes.The addition of manganese resinate to the silica gave the desired result. The commercial resinate is purified by treatment with ether or petroleum spirit, filtering, and evaporating the ether. The dry residue, which the author found to contain 9.80 per cent. of oxide, is powdered and kept in a stoppered bottle. The riiethod of determining the oxygen absorption of oils is as follows : From 5 to 10 grammes of the oil are weighed into a dish, and for 100 parts of oil exactly 2 parts of the resinate added; that is, for 10 grammes 0.2 gramme. The mixture is agitated on the water-bath until the resinate has dissolved, and then allowed to cool. One gramme of silica is weighed into a flat dish provided with a glass stirring-rod, and then drop by drop, by means of a pipette, 1.02 grammes of the resinated oil (1 grainme of oil + 0.2 grainme resinate) is added.The mass is intimately mixed, and spread aver the bottom of the dish, and is left at a temperature of from 17".to 25" C. for drying oils, and of 20" to 30" C. for other oils. The dish is weighed after six hours, and twice again in the twenty-four hours, and so on until the maximum is attained, the mhss being stirred up after each weighing. The inaxiinurn increase in weight, multiplied by 100, gives the degree of oxidation. The detailed results obtained with linseed, poppy, cotton seed, and earthnut oils are given in Tables I. and 11.106 THE ANALYST. I. Linseed-oil, Native. Density = 0.9357 a t 15" c. Linseed-oil, Native. Containing .5 per cent. iesin oil. 5 per cent.mineral oil. D=0.9323 at 15" C. Pure. I)=0%22 a t 15" C. Linseed-oil, La Plata. I) = 0.9304 a t 15" C. ? = 17"-23", 17" c. T = li"-14" C. r = 233-17" C. r-23"-17~ 0. 13.5 16.30 16.40 16.20 15.90 ... ... 14.80 ... . . . 1 i " C. c. 1243 16-10 16-60 16.50 15 -50 15.10 14-80 15.00 14-80 ... Hours. 6 22 24 30 48 72 96 120 144 216 4.95 16-70 17 -40 17.70 11.20 14-10 14-30 14-70 15-00 3.75 14-30 14-90 15.10 1.45 14-75 15-95 15.85 15-95 16.25 ... .., 16.65 11 -50 14.30 14-90 1-70 13-55 13-95 13.95 14.55 14-75 ... ... 15.35 14.80 14-60 .. . 13-80 ... ... 17.70 17 -70 17.30 ... ... 17-10 14.70 14.90 14-80 14-80 14-70 14-50 14.30 14.10 15-85 14-45 11. Cottonseed-oil, Containing cotton "stearin." 1) = 0.924 a t 15" C. Earthnut-oil, Mozambique. I)=0.916 a t 15" C.Poppy-oil. 1> = 0.9242 at 15" c. T= 28"-22" C, I!= 23"-17" C. T = 320-1 so, 34. 5"-14"C. Hours. 6 ... 22 ... 24 ... 30 ... 48 ... 72 ... 96 ... 120 ... 144 ... 4-8 13.60 13-90 14.50 0 -20 11.45 11.55 12-45 1-30 7.30 7 *60 8.20 0.10 5.70 6.20 7 -40 8 ~40 8-50 ... 0.80 3.50 3 30 4.70 5.30 6-10 6-70 - 0.20 - 0-20 - 0.10 0.80 3 -60 4-40 ... 4-80 14.10 13-00 12-50 12-00 10-40 14.30 13-35 8.20 6.50 6-50 12.75 8-00 ... I 7.80 ... 8.00 A general summary of results is given in the subjoined table. Earthnut-oil may be considered as intermediate bctween seirii-drying oils like cottonseed, and non- drjiag oils like colza and olive. For the latter it slightly more elevated temperatureTHE ANALYST. 107 Even then oxidation is not complete in a short should be employed (20' to 30" C,). time.111. Oils. Linseed, native ... ... ,, la Plata ... ... Hempseed ... ... ... Poppy, native ... ... Nut ... ... Cotton-seed with stearin . . . 9 , without stearin Sesame, Senegal ... . . . ,, Indian . .. ... Earthnut, African . . . ... ,, white ... ... Colza, native ... ... ,, Indian ... ... Olive ... ... ... ... $ 9 Density. 0,932 7 0.9304 0.9287 0.924 0.924 0.924 0-923 0.9215 0.921 0.916 0.916 0-9142 0-9137 0.9155 Degrees of Oxidation. 17*70-16.40 14.55-14.30 13-70 8-60 9.60-9.30 8-95-8.50 7-40 6.70 6-50 6.40 ? 5.90--5.80 ? 5-30 ? 15.45-15.00 14.50 - 13 -90 17.05 15.20 14.40 14.20 13.70 8-60 9.45 8.70 7.40 6.70 6-50 6-40 ? 5-85 ? 5.30 ? The degree of oxidation can be controlled by the Hiibl number, and in the author's opinion is in many cases more complete than the latter, since it shows at once the absorption power and the rapidity of oxidation.I n applying the method to the detection of vegetable oils in lard, it is preferable to employ the liquid fatty acids, for the separation of which the author recommends Halphen's process (ANALYST, xix., 282). C. A. M. The Bromine Heat-Value of Fats and Oils. J. A. Wilson. (Chem. News, 1896, 87.) - The author has examined Hehner and Mitchell's thermal process (ANALYST, xx., 146), and considers it in the main accurate and convenient. Using a test-tube packed in cotton-wool as his calorimeter, he found that with cocoanut-oil the rise of temperature multiplied by 5.5 gave at once the correct iodine value. With tallow, lard, butter, etc., it was necessary to add 1 before multiplying by that factor.This was shown in the following table : Rise of Temperature Calculated Observed with Bromine. Iodine Value. Iodine Value. Oil or Pat. Cocoanut-oil . . . ... 1.5 8.2 8.4 S.A. tallow . . . ... 7-0 43.2 44.0 Olive-oil (pure) . . . ... 14.0 82.5 82.0 Rape-oil ... ... ... 18.0 104.5 103 -4 W. J. S. The Use of the Calorimeter in Butter and Lard Analyses. E. de Schweinitz and J. A. Emery. (Jour. Anzer. Chem. Soc., xviii., 1896, 174-179.)- The samples of lard and butter which the authors were examining by the usual methods were prepared by washing, melting, filtering and drying at 100" C., and108 THE ANALYST. 9 1 12 14 16 18 19 22 26 27 2S 29 sent to Professor Attwater for combustion, without any information being given except that they were fats.The results of the analyses of butters and oleo- margarines are given in the following table : I. 1 i Original substance. Oakdale Manufac- turing Co., oleo- margarine Oakdale Manufac- turing Co., oleo- margarine Vermont Mann- facturing Co., oleomargarine Vermont Manu- facturing Co., oleomargarine Swift 8: Go., oleo- margarine Hammond Manu- facturing Co., oleomargarine Woodlawn oleo- margarine Elgin Creamery Butter Plains Va. Butter Armour 8: Co.'s Armour tc Co.'s best butter oleomargarine - I----- I-I- 0.8835 8'53 0,8906 8-00 0'8828 9.47 0.8874 9-00 0.8830 8-32 O'ti891 9.15 0.8880 9-23 0.8925 8-32 0.S979 11-43 023984 12-98 - - 0.42 0.35 0 -35 0.30 0 '22 0-22 0.35 11.10 8 ..5G 10'82 - 5.17 3.i6 5-31 3 $8 2.12 6.69 3 .SO 3-81 4-05 4.04 - .3 C 7 - i p v k -__ 1-36 2.59 1.33 1 -66 0.81 1-43 1-52 1.27 1'84 1-30 - ~ 5 -95 - 5 -67 3.68 2'19 6-21 3.68 3-64 4.93 3 -94 - ~ 23'0" 25.0" 25'0" 22.5" 24.0' 25.0" 22.5" 35.3" 36-1" 33.5" - Fat.al $ 6 CZ H 52.80 54-49 66.50 66.59 60.67 60.53 61.80 37.i5 36-86 41'20 49.91 9.599 9.620 9.795 9.649 9 -644 9.607 9.670 9-32i 9-362 9-320 9.601 5 i s Y ; alz g q s$ ~- Purple brown Purple brown Purple brown Purple brown No change No change No reaction No reaction Highly coloured Very highly coloured Highly coloured The figures obtained for butter-fat differ slightly from those given by Stohman, who found the heat equivalent, as determined by the potassium chlorate method, to be 9.192 small calories per gramme, while by the oxygen method it was 9.231 calories. The increase in the calories of mixtures of butter and oleomargarine was in proportion to the amount of the latter added. I n Table 11. the results were obtained by mixing Elgin butter (26) with Woodlawn Oleomargarine (22). 11. T,,eoretical I. Actual Combus- Theoretical Combus- tion Calories, tion Calories, per gramme. per gramme. Actual I. NO. NO. Sample. 2 E. and & W. ... 43-90 43.76 9-391 9.412 8 E. and 4 W. ... 48-01 49.77 9-416 9-498 I n the case of lards taken from different sources, the results are not so distinc- E. and 2 W. ... 54-40 55.78 9.491 9.584 tive, but, taken in conjunction with the iodine absorption, will be of use.THE ANALYST. 109 111. ANALYSIS OF LARDS FROM ARMOUR AND Co. Quality. Lard, leaf ... ... ... ,, caul fat ... ... ,, intestinal fat ... ... ,, head ... ... ,, trimmings . .. .-. ,, mixture of all fats ... ,, compound, 1st grade . 9 , , t 2nd grade ,, shield . . . ... ,, special pure ... ... Melting-point. Iodine No. _- 56.85 40.0" 58-61 40.7" 54.74 29.5" 68.79 - 65.57 - 63.86 __ 86.18 - 86-57 - 61.01 37.5" 63-63 Combustion Calories, per gmmme. 9-621 9.573 9.581 9.503 9.606 9.654 9.583 9.530 9.598 9.617 Cottonseed-oil, Becchi's Teat. None. Slightly darker. None. 9 9 9 9 9 , Purple brown. I , 9 9 None. C. A. M.

ISSN:0003-2654    

DOI:10.1039/AN896210102b

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年代:1896

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THE ANALYST. 109 INORGANIC ANALYSIS. On ths Estimation of Water in Silicates by the Borax Method. P. Jannasch and P. Weingarten. (Zeit. A ~ ~ o r g . CILewz., xi., 37.)-This is R modification of the process already described (ibid., viii., 352), which was designed to replace the method of water estimation where the mineral is opened out with plumbic oxide, and which was found to yield irregular results in the case of silicates rich in calcium. The new process permits of the portion of material operated upon being used for other subsequent determinations. 1-5 grainmes of borax, dried as described below, are placed in a platinum boat 7.5 c.ni. long by 1.5 deep, which is put into the middle of a thin-walled combustion tube 75 c.m. in length, followed by a plug of glass wool. To free the tube from the last traces of moisture it is heated gently in a combustion furnace for half an hour while a current of dry air is passed through, great care being taken to avoid fusing the borax.After this the tube is allowed to cool, the air current is stopped, and the weighed quantity of the substance under examination is mixed as rapidly and as iiztimntely as possible with the borax in the boat by means of a spiral of platinum. wire. The boat is pushed back to its former position, the glass-wool plug replaced, and the tube again connected to the air supply. The unweighed calcium chloride tube at the exit end of the combustion tube is changed for a weighed one, to the outer end of which the first tube is attached. The part of the tube containing the boat is then very gradually heated up, the remainder being kept as cool as possible by not covering it with tiles.When the borax is fused to a clear homogeneous glass in which bubbles are no longer being formed, the air-current is started once more, and the whole length of the tube is heated with a Bunsen burner to drive the moisture into the calcium chloride tube, which, after cooling to the temperature of the balance-room, is reweighed. Should fluorine be present in the substance analysed, a layer of granulated lead chromate 5 c.m. long, with a glass wool-plug at either end, is placed between the platinum boat and the exit end of the combustion tube, to absorb any volatile fluorides.110 THE ANALYST. The powdered borax employed in the process is prepared (Zcit.Anorg. Chenz.. viii., 352) by heating pure crystallized borax to incipient fusion in a platinum dish or crucible, allowing to cool, reducing to fine powder and finally heating to a dull red heat while the powder is stirred with a thick platinum wire. C. H. C. Volumetric Determination of Copper. M. Rupeau. (Bzdl. SOC. Pharnz. dc Bordeaux, October, 1895 ; through A m . Chiwz. AmZyt., i., 32.)-The author proposes the employment of a solution of picric acid, which gives with copper a precipitate insoluble in ammoniacal liquids. The standard picric acid solution is made by dis- solving rather more than 7.5 grammes of the acid in hot water, and, after adding ammonia (30 to 40 c.c.) till a decided odour is manifested, making up to 1 litre. After standing for some time, the solution, is filtered and standardized against a solution of 1 grainme of pure red copper, dissolved in nitric acid and made up to 100 C.C.with water (1 C.C. = 10 mgms. Cu). The picric acid is then run in, with constant agitation. So long as a green tinge is observed there is no danger of over- stepping the end point; but when this is approached the precipitate is allowed to settle, and the addition is proceeded with cautiously until a decided yellow tinge without any tendency to green is obtained in the clear supernatant layer of fluid. The titration of the solution under examination is performed in an exactly similar manner. When silver is present, 10 C.C. of ammonia must be added to the nitric solution to keep this metal in solution while titrating, and the same holds good for zinc as well.The oxide thrown down by the ammonia obscures the final reaction, but this may be obviated by adding a little tartaric acid. Iron is removed by simply boiling the solution, adding ammonia to precipitate the ferric oxide. I n the inost complex case likely to occur--i.e., one in which the copper is associated with all the four metals mentioned above-the method is as simple as Lead behaves differently. when iron is the only admixture. c. s. A Critical Examination of the Processes for the Estimation of Phosphoric Acid. C. Meineke. (Chem. Zeit., 1896, xx., 108.)-The author has already stated, some ten years ago, that it is perfectly possible by gentle ignition to convert the yellow ammonium phospho-rnolybdate into a form in which it can safely be weighed with the assurance of its containing a definite percentage of phosphorus.He has now reinvestigated his process, checking it on specinlens of phosphorite, on pure disodium phosphate, and on silver phosphate, and he finds that the phosphoinolybdic anhydride so obtained contains constantly 3.949 (&0.008) per cent. of P,O,; corre- sponding, therefore, to the formula 24Mo0, + P,O,, which (taking Mo = 95-9, P = 30.96, and 0 = 15-96) demands 3.944 per cent. The molybdate solution should be prepared by dissolving 150 grammes of the ammonium salt in 150 C.C. of ammonia (specific gravity 0.91) and 850 C.C. of water, pouring the whole into 1 litre of nitric acid (specific gravity 1.2). The liquid is heated to 90" C. for ten minutes, filtered from the molybdic acid, and preserved in the dark.THE ANALYST, 111 I n testing solutions poor in iron, the precipitation is so arranged that at least 5 per cent.of ammonium nitrate is present. To ensure this, ammonia (specific gravity 0.91) and nitric acid (specific gravity 1-4) are prepared, which, when mixed together in equal volumes, yield a moderately acid solution of the nitrate of about 53 per cent. con- centration. These are added in the necessary amounts in succession to the liquid under examination, and when the temperature has fallen to 50” C., the molybdate is added, the whole thoroughly stirred, and set aside till clear. If the solution, on the other hand, contains much iron, at least 10 per cent. of ammonium nitrate must be present, and enough free nitric acid to represent 5 to 10 per cent.of the 1-4 strength. The solution is heated to the boil, the inolybdate introduced, stirred up, and set aside. Further heating after the addition of the precipitant rnust be avoided. The precipitate should be pale yellow, and the liquid must also be light in colour. It is washed with a liquid consisting of 100 C.C. each of the same acid and ammonia diluted to 1 litre with water. il final rinse in pure cold water is given, followed, if desired, by alcohol and ether, and the filter is then dried. I t is ignited in a porce- lain basin or crucible over an argand, or in a mume, at a temperature which is not visibly red by daylight. When hot, the residue has a somewhat grayish colour, but when cold it is blue-black.I t must be free from yellow or green particles, and also froin free iiiolybdic acid ; and it should be cooled in the desiccator. The author has also examined the statement that the presence of ammonium chloride in solutions containing much iron, which are to be precipitated by molybdate solution, is to be avoided. A series of careful experiments show that this substance, even when present in abnormally large amounts, is entirely without action on the results. The remainder of the paper contains a long and elaborate examination of the two processes-Maercker’s and Wagner’s--for the estimation of phosphoric acid by magnesia mixture when following the molybdate precipitation. The former neutralises the ammoniacal solution of the yellow precipitate, introduces the magnesia mixture, a d finally adds ammonia in 24 or 3 per cent. excess.Wagner prefers to add the reagent direct to the alkaline solution, which should contain the same amount of free ammonia. Both processes are liable to several errors : the pre- cipitate is somewhat soluble, it is apt to vary in composition, and, according to the temperature of ignition, greater or less loss of phosphoric acid iiiay occur. Neubauer has published a table of corrections for this last source of error, but it cannot be considered exact. The present author, when using Wagner’s process, prefers to ignite the precipitate gently, weigh it, ignite again over the blow-pipe to constant weight (10 to 15 minutes) and weigh once more, The original precipitate, consisting of an indefinite mixture of pyro- and meta-phosphate, suffers a loss of P,O, corre- sponding to the Mg(PO,), it contains ; and if this loss be multiplied by 2.56, and the weight so obtained be subtracted from the original, the remainder expresses the true amount of pyrophosphate in the compound.I n this manner the quantity of phosphoric acid in the precipitate can be determined exactly : the yield usually being a trifle above the theoretical. It may be observed that without correction, Wagner’s process gives sufficiently exact results for many practical purposes, such as the analysis of manures : for when 1 gramme of substance is taken, the phosphoric acid comes out only about 0.2 per cent. too low.112 THE ANALYST. With Maercker’s modification, the original precipitate i s apt to vary in composi- tion still more ; but good results are to be obtained by preventing the precipitation of the magnesium phosphate from occurring too early during the addition of the reagent. Experiments show that it is better to effect this by means of ammonium citrate than by a large excess of hydrochloric acid ; and the process is best arranged 60 that the liquid remains clear until half of the necessary amount of magnesia mixture has been run in. I n all cases the precipitate must be ignited strongly to constant weight, in order to remove the niolybdic acid which is always present. F. H. L.

ISSN:0003-2654    

DOI:10.1039/AN8962100109

出版商:RSC    

年代:1896

数据来源: RSC

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112 THE ANALYST. R E V I E W . PLLICTICAL STUDIES IN FERMENTATION, BEING CONTRIBUTIONS TO THE LIFE HISTOI~Y OF MICRO-ORGANISMS. By EMIL CHH. HANSEN, Ph.D. (London: E. and F. N. Spon.) This work, which is a translation of the last edition of Dr. Hensen’s widely- known ‘‘ Untersuchungen ails der Praxis der Giirungsindustrie,” together with some additions, presents, for the first time in the English language, a collective ~-dss’z~~~zP of the author’s work in connection with the morphology and physiology of the fermen- tation fungi, and will in this form doubtlessly be welcomed by many who have been hitherto uuable to peruse it in the original. I t contains a summary of Dr. Hansen’s investigations into the life history of the fungoid organisnis which play such an important part in the great fermentation industries, especially in those devoted to the production of beer.Dr. Hansen dis- covered some twelve years since that differences and distinctions, quite as pronounced as in the more highly-organized plants, were to be found in these lowly organisms, and that some of the species were able to exert quite as baleful an influence on the fermentations as the bacterial organisms. This discovery led to Dr. Hansen’s great and important reform, which consisted in the introduction into fermentation operations of yeasts derived from a single cell, and therefore consisting of one species or variety only. This principle has proved itself of enormous value to all the fermentation industries; and though it was originally applied only to those engaged in the pro- duction of beer, has been extended to other branches, such as distilling, wine and cider making, the manufacture of pressed yeast, etc., and even to those, such as the manufacture of cheese and of tobacco, in which fermentations caused by bacterial organisms play an important part.Details of the various operations required for the isolation of the single yeast cell, and of cultivating from it yeast in quantities sufficiently large for practical application, are given, together with much inforiliation of a highly useful nature to the practical brewer. I n addition to this, much will be found which is of great interest to the pure scientist, not the least being the account of the author’s experiments, by means of which he has succeeded in effecting artificial variations of a more or less permanent nature in a number of the yeast fungi. Altogether, the work is one of the most remarkable of modern timeti, and is of such vast importance, that no one engaged in any of the fermentation industries can well afford to be without it. The task of translation, which has been entrusted to Dr. A. K. Miller, has been excellently performed. W. J. S. Price 12s. 6d.

ISSN:0003-2654    

DOI:10.1039/AN8962100112

出版商:RSC    

年代:1896

数据来源: RSC