196 THE ANALYST. MONTHLY RECORD OF ANALYTICAL RESEARCHES INTO FOOD. AT the meeting of the American Association for the advancement of Science, Prof. A. R. Leeds reported that he found the composition of human milk, on using every precaution, to be : albuminoids varying from -5 to 4.25 per cent., lactose from 4.1 to 7.8 per cent., and fat from 1.7 to 7.6 per cent. The appearance and specific gravity of human milk, according to the same authority, never give any real index of its composition. At the ~ a m e meeting Professor Atwater read a paper on the chemistry of fish. Flounder is the least nutritive of fishes ; while the salmon, when fat, is the most nutritive. Oysters have least nutritive matter among the invertebrates ; and northern oysters are more nutritive than those from the south, The flesh of fish contains less fat and more water than that of vertebrates.Digestive ferments act upon the flesh of fish in the same may as upon that of the vertebrates, about ninety-eight per cent of the albuminoids being digested in both cases. As ordinarily found, fish gives from five to twenty per cent. of edible matter. I n the last Zeitschqtfur AtaalzJtische Chencie, J. Uffelman makes an advance upon Fuch’s idea as to the presence of nitrates in milk, proving the addition of impurewater, and he has further amplified the matter so as to take into consideration the presence of ammonia and nitrous acid. He adds diluted acetic acid to 350 C.C. of milk until the caaeine is entirely thrown down ; 100 C.C. of the filtrate are then mixed with three drops of hydrochloric acid, boiled up, allowed to cool, and filtered.Of this new filtrate 50 C.C. are rendered faintly alkaline with pure potassium hydrate, filtered, clistilled, and the dis- tillate is tested with Nessler’s reagent. To the remaining 50 C.C. are Rdded sodium hydrate and carbonate, the mixture is filtered, and tested with Nessler’s reagent. The residue-of the liquid filtered from the acetic acid precipitate is boiled and filtered. 30 c.c are tested with meta-phenylen-diamine, and another 30 c.c, with zinc-iodide-starch paste for nitrous acid. The remainder is utilised for detecting nitrates by means of diphenyl- amine. A little ci*ystalline diphenylamine is dissolved in a white capsule in about 1.5 c. C. of pure sulphuric acid (full strength) and three t o four drops of the milk atrate are added.I n presence of much nitric acid there is foirned almost immediately a blue zone, which quickly extends. If there is little nitric acid the colour appears only after some time. I f the blue colour does not appear, the experiment is successively repeated with portions of the milk-filtrate, concentrated respectively to one-third, one-seventh, and one- tenth of the original volume. Neither ammonia, nitric nor nitrous acid, is ppesent in normal milk, but all t h e e may be introduced by sophistication with inipure well-watep, In the same volume M. Vitali points out that when funel oil (amylic alcohol) hae been separated from spirit by Betelli’a method of shaking up with chloroform, its presence in the residue may be proved as follows !-If the reaidue Buepected to be arnylie alcoholTHE ANALYST.197 be poured upon sulphuric acid, and then cautiously stirred with a glass rod, a play of colours is produced, commencing with dMy red and passing through violet to azure blue, and lastly to green. The addition of a fern drops of ether makes the colours more brilliant. rChe following is a description of a water bath designed to keep the water at a constant level by Dr. E. Mascarenas y Hernandes, in La ATatzcre :- The reseivoir for water is a bottle tightly stoppered and through the stopper of which two glass tubes pass bent twice at right angles, one terminating just below the stopper, and having its outer limb ending at the exact level at which the water in the bath is to be kept, while the other tube extends to the bottom oi the reservoir with one limb, and with the other to some distancedown the neck of the water- bath.As soon as the siphon has been started, the water will flow from the reservoir until the end of the shorter tube becomes closed by the water, when the flow mill cease, to begin afresh L~EI soon as the level sinks. In April last an attempt was made by H. Rabourdin, to estimate the amount of adulteration in commercial peppers, by olive stones and husks, and other similar hard bodies. It was published in the French Jourfial de Phamaoz'e, and has been hitherto passed over without much notice, but we have found it very useful as an aid in the microscopic examination of pepper, and to a certain extent fairly quantitative for other hard adulterants besides those named.It is as follows :- A gramme of the sample is boiled continuously €or an hour in 100 grammes dis- tilled water and 4 grammes sulphuric acid, adding more water from time to time to make up for the loss by evaporation. The flask must be supported by the neck or it will be fractured by bumping. After boiling for an hour the liquid is allowed to cool, and poured upon a plain double filter which has been previously well dried and tared. m e n the pepper contains olive-kernels they fall to the bottom of the flask, and when the liquid is poured upon the filter they are found upon the sides of the flask in reddish fragments, more or less plentiful. This character already is decisive, since pure pepper never gives these dense, reddish fragments.The flask is repeatedly rinsed out, and the iilter with the residue is perfectly washedwith boiling distilled water. It is then dried and weighed very carefully. The weight of this total residue forms the coe@cimt of the pepper, This value is vayiable for every kind of pepper, but for all pure kinds within ve~y naprow limits, and is strikingly increased when the pepper is adulterated with kernels or shella. The average valtte for pure peppers of commerce, 0.35. On the other hand, that of tho olivebkemels is on the average 0.745, and that of the husks or shells 0.70.--_THE ANALYST. TEE DETERMINATION OF TEE ALBEMINOIDS IN HUMAN MILK E. PPEIFFER. (Communicated by the Author to the Zeitschrift f. Physiol. Chemie, 8.259.) THE author's researches deal, firstly, with the precipitation of caseine by acids ; and, secondly, with the determination of the total albuminoids, according to the methods hitherto proposed.I- 198 As regards the first point, the author shows that in the precipitation of caseine; according to his method (viz., that of digestion for 10-15 minutes at 50-55"R. with dilute hydrochloric acid), other acids, diluted to the requisite strength, may be substituted for the hydrochloric acid. Thus, lactic acid (1 c. c, pure acid of sp. g. 1,0065 to 40 c. c. H,O), acetic acid (2 c. c. concentrated acid to 100 c. c. H,O), and sulphuric acid (2 c. c. conc. acid to 100 c. c. H20) produce, when added in drops, a pronounced coagulation. Dilute phosphoric and nitric acids do not give such good results.With the right strength of acid the coagulation takes place at a temperature as low as 30-40°R., which proves that a high temperature is not essential to, but only hastens the coagula- tion. The precipitation is best when the acidulated inilk is placed in water at a temperature of 25-30°R., and then slowly warmed to 45OR. The author then proceeds to compare (as regaids the results obtained) his ( ( hyilro- chloric acid method" (Zeitsch fur Anal. Chem. 22, 14) for the determination of tho total albuminoids, nith the method in which they are precipitated by tannin, and the one in which an equal volume of alcohol is used. Following the directions given by Biedert for the tannin method, the author used n 10 pel* cent. aqueous solution of tannin, of which 2-4 c.c. were found necessary for 10 grms. of milk. Sufficient tannic acid having been used, the precipitate, containing the total aIbuminoids and fats, was easily Btered and mashed xithout loss. It appears, howeveie, that its weight, after the renioval of the fats, cannot be used for the calculation of the total albumiiioids, as it contains variable quantities of tannic acid. Besides this, the filter paper is liable to become very weak, especially when much tannin is used, and, on drying, to fall to pieces. The author finds more serviceable the method depending upon the precipitatiou of the albuminoids by alcohol, more especially because it allows of an approximately separate determination of the caseine and of the albumen. The greater part of the albuminoids, which the author regards as essentially caseine, is precipitated by adding an equal volume of cold absolute alcohol.Care must be taken not to add it in too large a quantity, as the precipitate is not thereby rendered more coniplete, whereas, on the other. hand, a larger quantity of butter-fat is dissolved, which necessitates afterwards a separate fat deteimination in the filtrate. For the same reason, the autlior reconmellds washing the precipitate with an alcoholic solution, coutainiiig equal volumes of absolute alcohol and wateii, the washings, however, should not exceed the volunie of milk taken. The filtrate, together with the washings, is, after the addition of a little water, evapo- rated until no more alcohol remailis ; it is then boiled, and the precipitate, thus pz*oducsd,THB ANALYST.199 collected upon the filter, dried, and weighed. I n one part of the filtrate, the sugar may be estimated by any of the ordinary methods, while the albuminous residue ’’ can be determined by precipitation with tannin. Analyses of the same milk, carried on simultaneously, on the one hand by the alcohol, and on the other by hydi*ochloiic acid method, did not, however, completely agree. The results are mostly higher for both the caseine and the albumen, with the hydro- ohloric acid method, Le., the sum of the caseine and the albumen is generally greater than in the &oh01 method, BO that a less quantity of the ‘( albuminous residue ” remains to be precipitated by tannin. For this reason the author prefers his method. The author adds to hia former communications, the observation that he has found the temperature S0-55Ql%.the best for the coagulation of the caseine. I?. H. H. Bonn, 21st October, 1884. f)r. Henry LeffrYrann has published a series of analyaes of butter, which we sum- marise from his article in the Chmical News, chiefly because they axe performed by a process not uaually employed by British analysts. Dr. Lef€mann uses the method of Koettatorfer in preference to any other, Viz., ascertaining the quantity of real potassium hydrate required to saponify the fat, and he also takes advantage of the odour of butyric ether given off during limited sapon2fication with alcoholic soda, to prove the existence of butter at all. His results are expressed in terms of the amount of standard acid to which one gramme of the fat is equivalent in action on alkali. Divesting his table of unimportant particulars, we have the facts that :-- Genuine butters took from 5.5 to 6 9 acid, and gave a powerful ethereal odour. Doubtful ,, ,, ,, 5.0 to5.1 t P 9. feeble ?P >t 4‘Bogu~” ,) ,, ,, 4.3 to4.9 ,? ?, 90 ?? ?? Although there is nothing very novel in the above information, still we put it on record, as every faot tending to throw any light on food analysis, should be recorded in our aohmns.