^36 



Proceedings of the Royal Irish Academy, 



LVII. — On the Chemical Changes which take place in the Potato 

 DimiNG THE peogkess OF THE DisEASE. By the E,Ey. John H. 

 Jellett, B.D., S.F.T.C.D. 



[Eead May 22, 1876.] 



The olDJeet of the experiments described in this paper was two-fold, 

 namely : — 



1. To ascertain whether there be any development of sugar in the 

 tuber, and if so, what is the kind of sugar developed. 



2. To ascertain whether there be any perceptible change in the 

 quantity of nitrogen. 



The experiments were conducted as follows. Pour specimens were 

 taken from the same variety of potato, viz. : — 



1. Perfectly sound potato. 



2. Apparently sound part of potato in which the disease had just 

 begun to appear. 



3. Apparently sound part of potato in which the disease was far 

 advanced. 



4. Discoloured part of diseased potato. 



These specimens, having been carefully weighed, were severally 

 grated, then subjected to a strong pressure in a screw press, and 

 finally exhausted with spirit. 



The fluid so obtained was filtered, to remove the albumen and 

 starch, and (the spirit having been distilled off) was diluted with 

 water to a known bulk. It was then examined in the usual way for 

 sugar. The result is given in the following Table. 



Table I. 





I. 



II. 



III. 



IV. 



Water (percentage in tuter). 

 Nitrogen (do.) . . • . 

 Sucrose (do.) 

 Glucose (do.) 



73-09 

 •27 

 •08 

 •42 



77-24 

 -35 

 •29 

 •65 



80-04 



-31 



1-14 



-76 



79-28 

 •25 

 •21 

 •40 



Por the second part of the experiment four specimens, selected as 

 before, were carefully weighed and dried. They were then burned in 

 the usual way, for the purpose of estimating the quantity of nitrogen. 

 The results are given in the following Table. 



