- 4 6- 



repeated precipitation with alcohol remained perfectly clear on 

 boiling; yet, previous to boiling, the same solution was strongly 

 active, rapidly changing tincture of guaiac to dark blue, and the 

 clear brown resin from the lac to a hard, black, insoluble sub- 

 stance. ^ 



Solutions of the gum were treated with acetic, hydrochloric, 

 nitric and sulphuric acids of various strengths and with varying 

 degrees of heat, but each failed to separate the nitrogenous sub- 

 stance from the gum. In one experiment the solution was boiled 

 for half an hour with a dilute sulphuric acid, precipitated with 

 alcohol, dissolved in water and reprecipitated with alcohol, 

 washed until free from sulphuric acid, and dried in an 

 exsiccator. This still gave the pyrrol reaction. Fractional pre- 

 cipitation was tried without apparent change in the relation of 

 gum to nitrogen. Cold saturated solutions of magnesium sul- 

 phate, ammonium sulphate and sodium phosphate were tried in 

 vain. Various modifications of Almen's solution of tannic acid 

 were tried, but in no case was there any separation of nitrogenous 

 from non-nitrogenous substance. Numerous precipitates were 

 obtained, but in every case the precipitate contained both gum 

 and nitrogen in apparently the same proportion as before. The 

 dry powdered gum was heated for two hours at temperatures 

 varying from 100 to 160 C. and tested both by boiling alone 

 and with acids, but no separation occurred. 



EXAMINATION OF OTHER GUMS FOR NITROGEN. 



A number of the following samples were prepared by stu- 

 dents and kindly furnished by Professor Tschirch from his col- 

 lection. The remainder were prepared by the writer. In the case 

 of the gum-resins the resin was removed by extracting with alco- 

 hol, the gum dissolved in water and precipitated by alcohol, puri- 

 fied by repeated precipitation and dried in an exsiccator. The 

 acids were prepared by the same method, with the exception that 

 the solutions were acidulated with hydrochloric acid each time 

 before precipitation, and the precipitate finally washed with alco- 

 hol until free from hydrochloric acid. Nos. 14 and 15 were pre- 

 pared by dissolving the tragacanth in a warm solution of sodium 

 hydroxide, precipitating with alcohol and dissolving in water, 

 and reprecipitating with acidulated alcohol. 



Each sample prepared without heat was tested for enzyme, 



