BUREAtr OF CHEMISTRY. 581 



large amounts of arsenic. From evidence secured from dealers it 

 seems fairly avoI! estahlislied that arsenic enters the gelatin thronuh 

 the raw material from which it is made or from acid used in the 

 process of manufacture. Hides intended for the manufacture of 

 leather are often treated Avith arsenical preparations in order to de- 

 stroy' the germs of contagious diseases, and when, through accident 

 or carelessness, the trimmings from such material enter the gelatin 

 stock, contamination with arsenic results. As a consequence of the 

 anal^'tica] pr()l)lems resulting from the estimation of arsenic in gel- 

 atin and in a great variety of other substances, it was found neces- 

 sary to evolve rapid and accurate methods for this determination. 

 Existing methods involve a long and tedious destruction of organic 

 matter before the arsenic can be separated and determined. A method 

 has been devised at this laboratory whereby this procedure is re- 

 placed by more rapid and accurate processes, and new means have 

 been" found by which amounts of arsenic ranging between very small 

 and very large proportions can be conveniently estimated. (See 

 Circular 102, Bureau of Chemistry.) This last process dill'ers from 

 those already in vogue in that the old method provided for the esti- 

 mation of small amounts, ranging from traces to about 100 parts per 

 1.000,000, and for amounts greater than one-tenth of 1 per cent. 

 The new method provides for the determination of amounts between 

 the limits just given. 



Colors. — Investigation of methods for separating and identifying 

 coal-tar colors in foods has been continued, and much new informa- 

 tion on this sui)ject has been ol)tained. 



Vineg.\r. — The study of vinegar has been continued during the 

 past year by a chemist who has visited various plants where vinegar 

 was made, a thorough examination being conducted of the initial, 

 intermediate, and finished products, with a view to securing such 

 data as will enable analysts to detect the extremely ingenious and 

 sometimes baflling methods of sophistication practiced by some man- 

 ufacturers. A prominent feature of the vinegar work has been the 

 determination of formic acid in vinegar, adulterated with acetic acid 

 made from pyrol igneous acid. 



Lkad. — The analytical estimation of lead in phosphate and alum 

 baking powders has l)een studied at this laboratory during the past 

 year with satisfactory results. 



A. O. A. C. WORK. — Members of this laboratory have cooperated 

 with the Association of Oflicial Agricultural Chemists in the study 

 of analytical metliods for cotFee, coco and chocolate, sjiices, colors, 

 vinegar, flavoring extracts, heavy metals, moisture, egg noodles, and 

 condiments. 



Drug work. — A new drug laboratory was established during the 

 past year and the work in this line has greatly increased. The in- 

 vestigation of asafetida has been continued. Color reactions for the 

 purity of this drug have been established, as well as a quantitative 

 constant in the lead number of the purified resin. Tlie semicarbazid 

 method for benzaldehyde has been elaborated and applied in general 

 to the aromatic aldehydes with satisfactory results. Particular at- 

 tention has been paid to the estimation of morphin, and the investiga- 

 tion has shown that the morphin sulphate used in hypodermic tablets 

 is usually adulterated with codein. The separation of morphin, 

 codein, and atrophin has been studied and a method devised. The do- 



