_-2 9 



Yoshida has named this substance oxy-urushic acid and giv- 

 en it the formula C 14 H 18 O 3 , but as it has none of the properties 

 of an acid I have called it oxy-urushin. Owing to the presence 

 of nitrogen I am loth to suggest a change in the formula. That 

 nitrogen is present has been proved (beyond doubt) by the meth- 

 ods more fully given under gum-enzyme. That nitrogen is in 

 actual combination is supported by the fact that it is separable 

 only by fusing with dry fixed alkali, or incompletely by long 

 boiling with a solution of fixed alkali. Owing to the small amount 

 of nitrogen present, a very slight error in estimation would ma- 

 terially affect the results from calculation of a molecular formula. 



The Kjeldahl method could not be used for the determina- 

 tion of the nitrogen, hence the necessity of using the Dumas 

 method. The principal objection to this method is the difficulty 

 of completely removing the air from the fine copper oxide. After 

 numerous experiments the substance was finally mixed with cop- 

 per oxide in fine powder and placed in a copper boat which was 

 then placed in the combustion tube and the air removed by car- 

 bon dioxide, generated from sulphuric acid and potassium car- 

 bonate by Thiele's method 15 . The results were very concordant. 



For calculation of the empirical formula only those results 

 which were obtained without heating with alkali, can be used, 

 as alkali causes a loss of nitrogen. Therefore the mean from I 

 and 3, corrected for ash, was used as follows: 



Mean from Calculated for Ash Calculated for 



i and 3: Free Substance CiogHiag^O^ 



C.... 71.777 72.137 72.206 



H.... 8.118 8.156 8.202 



N.... 1.644 1.652 1.656 



Ash.. 0.5 



o .*.... 17.936 



The above formula was calculated from the benzin-insoluble 

 portion which represents only 22% of that portion of the lac 

 that is soluble in alcohol. The remaining 78% which is soluble 

 in benzin could not be obtained in a dry form, or changed into 

 its end product without the use of reagents which caused a loss 

 of nitrogen; hence no attempt was made to calculate a formula 

 from the results obtained by combustion. The results obtained 

 in 6, 7 and 8 differ so much from those of 2 and 3 that it would 



15 Ann. der chem. 253, 1889, p. 242. 



