146 EXPERIMENT STATION. [Jan. 



dilute phosphoric acid into bromine water. The excess of bro- 

 mine was then boiled oli" and the sulphuric acid formed deter- 

 mined by precipitation with barium chloride. The distillation 

 was conducted in the jiresence of carbon dioxide, which served 

 to prevent oxidization. Dilute copper sulfate solution^ was 

 used to purify the sulphur dioxide. Since it was necessary to 

 employ relatively large amounts of the sample for distillation, 

 it was found convenient to place the distilling flask on an oil 

 bath to prevent burning. The following table gives the result 

 of several determinations : — 



Number of Sample. Sulphur Dioxide (Per Cent.). 



1, 

 2, 



3, 

 4, 

 5, 



.UUOU 

 .0008 

 .0040 

 .0006 

 none 



lilaiik .UUO.> ill each case. 



The results of these various analyses show that the amount of 

 sulphurous acid in the sam])les of gluten feeds tested was small, 

 and it can be assumed that practically all of the sulphurous acid 

 originally added has been driven off or oxidized to sulphuric 

 acid. Formerly the United States government allowed the addi- 

 tion of sulphur dioxide to foods at the rate of 350 milligrams 

 per kilogram, or .035 of a gram per 100." This decision was 

 later amended,^ pending determination by the referee board, 

 and at present calls for the labeling of all foods containing even 

 small amounts of suljihur dioxide. 



4. Coloring Matter. 

 In the work presented on coloring matters no attempt has 

 been made to determine the individual dye or combination of 

 dyes used, but rather to ascertain whether the added color was 

 one of vegetable or coal tar origin. The method for the detec- 

 tion of artificial coloring matter in gluten feeds recommended 

 by Gudeman^ is not applicable in those cases where the sub- 



1 Winton and Bailey, Journal American Chemical Society, Vol. XXIX., No. 10, 1499. 



- Food inspection decision No. 76, July 1.3, 1907. 



' Food inspection decision No. Si), Feb. 28, 1908. 



* Journal American Chemical Society, Vol. XXX., No. 10 (1908), 1623. 



