BUREAU OF CHEMISTRY. 577 



An investif^ation has also been made of the methods of manufac- 

 ture in a hirge number of such establishments and a study made of the 

 various raw materials used. 



Gelatin. — For the investigation of the manufacture of gelatin dur- 

 ing the past year arrangements were made with a number of manufac- 

 turers of gelatin to allow their methods of manufacture and the effects 

 of various forms of treatment upon the finished product to be studied. 

 The bacteriological laboratory cooperated, giving special attention to 

 the source of bacterial infection during the process of manufacture. 

 A field laboratory was established in first one, then another, large fac- 

 tory where various forms of raw^ material were used. A careful study 

 has been made regarding the effect of the use of sulphurous acid on 

 the content of bacteria in the finished j^roduct and al^o on the occur- 

 rence of harmful metals in the product. 



During the last year attention has been given to the addition of 

 arsenic and lead to food incidentally in the method of manufacture 

 and without intention or knowledge of the makers. Arsenic has been 

 found to be added from its presence in coloring matter, shellac, and 

 such products as phosphates by reason of the material from which 

 prepared. Lead is almost universally contained in the tartaric acid 

 on the market, and a study was made of the manufacture of tartaric 

 acid and cream of tartar. The presence of lead was found to be due 

 to the use of lead receptacles and pipes and lead-lined vacuum pans, 

 and to the fact that in the attempt to remove it in the manufacturing 

 establishments the solution to which hydrogen sulphid is added is too 

 concentrated and at too high a temperature. 



Food colors. — A special feature of the work of the food-inspection 

 ]al)oratory has been the examination of colors, especially work on 

 samples where disputes have arisen as to the identit}^ of the coloring 

 matter present. Further, the study of the methods of detection of 

 colors has been continued, and a large number of fruit samples pre- 

 pared for comparison with samples which are brought in for exam- 

 ination. During the year a set of the coal-tar dyes, which have been 

 used in food products, was prepared and furnished to all the branch 

 laboratories. Much of the time was given up to the study of the 

 identification of the coloring and facing materials used on teas, for 

 the information of the Treasury Department. 



The question as to the normal ash content of certain samples of 

 imported red pepper, notably the Spanish pimenton, was raised, and 

 in order to decide whether or not the standard used by the department 

 in judging these products was correct IGl samples were examined, 

 with the result that it was found that the limit on ash was decidedly 

 too low for certain Spanish ])roducts which were perfectly normal in 

 thoir composition; as a result it has been necessary to raise the stand- 

 ard of ash. 



Branch Laboratories. 



general tabular statement. 



The 22 branch laboratories maintained at the principal ports of 

 entry for imported food and drug products and at the centers of dis- 

 tribution of domestic food and drug jM-oducts are concerned jirinci- 

 pally with the work of enforcement of the food and drugs act. 



70481°— AGR 1912 37 



