Dec, 191()J Boric Acid in Some Foods G7 



first to measure the boric acid by comparing the colors in tubes 

 which contained about fifty cc. of solution. The standards 

 were boric acid dissolved in weak hydrochloric acid to which 

 was added some standard turmeric solution. In other tubes 

 were hydrochloric acid solutions of the iron free ash of the 

 sample to which a standard solution of turmeric had likewise 

 been added. The Schriner-Schorey colorimeter was used. The 

 quantities of boric acid in the fruits were so small, however, 

 that the depth of color given with the standard turmeric solution 

 was too weak to give accurate comparison. 



The method finally used was one for estimating very small 

 quantities of boric acid in organic substances described by G. 

 Bertrand and H. Agulhon in Comptes rend. 1913, 157, 1433- 

 1436 and reported in the Analyst for 1914. Ten or twenty 

 grams of animal substance or one gram of vegetable substance 

 are mixed with sodium carbonate and ignited to ash which 

 need not be white. To the ash 5-10 cc. of phosphoric acid are 

 added and the whole transferred to a flask with 20 cc. of methyl 

 alcohol. The mixture is distilled and the distillate is collected 

 in a platinum dish containing 2 or 3 drops of sodium hydroxide 

 solution. A second portion of methyl alcohol is added and the 

 second distillate collected with the first. The combined distil- 

 lates are evaporated to dryness and the residue taken up with 

 3/2 cc. of tenth normal hydrochloric acid. A strip of turmeric 

 paper 3 mm. by 45 mm. is put into the hydrochloric acid solu- 

 tion so that about 20 mm. extends above the edge of the con- 

 taining vessel. The whole is set aside for 24 hours at room 

 temperature or for 3 hours at 30 degrees. The length of the 

 colored strip at the outer end of the turmeric paper is compared 

 with a similar colored strip on paper immersed in solutions 

 containing known amounts of boric acid. The method depends 

 on the formation of a volatile compound of methyl alcohol and 

 boric acid which is distilled over and the second portion of 

 alcohol is used to make sure that all of the boric acid is taken 

 over. 



The standards for comparison are made by dissolving known 

 amount of boric acid in weak hydrochloric acid. The standards 

 must be treated exactly as the sample is treated — the same 

 quality of turmeric paper must be used, it must remain in the 

 solution the same length of time as the paper remains in the 

 solution of the sample and the turmeric paper must be placed 

 in each solution simultaneouslv. If these conditions are fol- 



