Action of Chemicals on Potato- Tuber s. 281 



Immersion for from three to six hours in either 5 per cent, 

 or 10 per cent, sulphuric acid induces marked retardation of 

 growth. In certain cases (Experiments 2. 7, 7a, 7b, 10) actual 

 su})pression of the sprouting powers of the tubers resulted. 

 These results, although variable, are not surprising, when the 

 variability of the material, and the possible individuality pos- 

 sessed by such biological material, are given due consideration. 



The effect of the 10 per cent, solution is in no way doubtful ; 

 a steep in this concentration of acid, of 20 hours' duration, 

 effectively and conclusively destroys the vitality of the buds of 

 the treated tubers. 



In addition to the numerical data in the above tables the accom- 

 panying Plates LVII., LVIII., LIX. (planting and storage exper- 

 iiients) indicate both the retardation and the destructive influence 

 exercised by sulphuric acid when used as a steeping reagent. The 

 storage quality of these tubers was in every instance unim- 

 paired. In the above experiments, after two months' storage, it 

 was impossible to differentiate them from the untreated but 

 otheiwise similar tubers, which served as a control iu these 

 storage tests. 



In experiments 7, 8 and 11, the amount of acid in definite 

 volumes (100 c.c.) of solution was determined at the commence- 

 ment and termination of the experiments ; these results are 

 given below : — 



Expt. Grains of acid per 100 c.c. of solution Decrease in amounts 



At commencement At termination of acid per 100 cc. 



of steeping- of steeping- of solution. 



7 - 9.408 - 9.359 - 0.049 grams. 



8 - 9.408 •- 9.408 - 0.00 grams. 



9 - 9.506 - 9.408 - 0.098 grams. 



It is evident that the amounts of acid which diffuse from the 

 steeping medium into the tubers are relatively minute. 



Since in each of these experiments 1.500 c.c. of acid solution 

 were used, and the average weight of (1) 5 tubers was approxi- 

 mately 1.650 grams, all the necessary data are available for 

 calculating the apparent percentage weight of acid absorbed. 



Taking for example t^xp^M-iment 9, we liaM- weight of acid 

 withdrawn from 1.5C0 c.c. = 15 x 0.098 grams. 



