Bitter Pit in Apples. 16 



With Statesman apples therefore, the mercurii' chh>ride eeases 

 to exert any poisonous action at — 1 tleg. C in a concentration of 

 1 per million, but continues to show a poisonous action at 25 — 26 

 <ieg. C. in a concentration of 1 in 10 millions. Comparing all the 

 results, "\ve may say that a fall of temperature of 25 deg. C. lowers 

 the poisonous concentration 10 to 100 times. 



Using copper sulphate and Yates' Pippin apples, the results were 

 obtained as given in Table II. 



In this case copper sulphate in a coueeiitration of 1 in Id, 000 

 exercised about the same poisonous action at — 1 deg. ('.. as a eon- 

 oentration of 1 per 1,000,000 did at 28— .30 deg. C, and the latter 

 concentration exercised no poisonous action at all at the lower tem- 

 perature. Under the conditions of the experiment therefore, copper 

 sulphate was a hundred times as poisonous to the pulp cells of apples 

 at 28—30 deg. C. as it was at 0—1 deg. C 



The influence of diffusion. 



Temperature exercises a most important influence upon tlie rate 

 of diffusion, and hence also upon the rate at which the poison in 

 solution would diffuse to the prepared spots on the apples tested 

 The rate at which the molecules of the dissolved substance reach tlie 

 receptive surface is an important factor in determining the concen- 

 tration at Avhich a poisonous action can be exercised. 



Thus in the case of Yates' Pippin apples floated on mercuric chlo- 

 ride solution at 15 deg. C. for thiee days, the poisonous limit was 

 reached with a concentration of one gram in 10 million eubie 

 centimetres of water. On the other hand, if tlie poisonous solution 

 was allowed to trickle directly over three prepaied spots, three times 

 daily for three days, from a fine tube at a temperature of 11: — 15 

 deg. C, a slight poisonous action was still shown with a concentra- 

 tion of 1 gram in 1000,000,000 c.c of water. 



Yates' Pippin. Mercuric chloride, 1 litre of solution run over 

 three prepared spots, three times in three days. Tempei ature 

 14 — 15 deg. C. Trickled directly over prepared spots from fine 

 tube. 



1 per 1(X),0(X),()0(J - No distinct signs of poisoning, but aft-r 



1 week in air, siipei-ficial browning 

 with Idacker rim to each prepared 

 spot. 



1 per 10U.(KK>,(XM').(HK) - No signs of poisoning, and after one week 

 in air no distinct signs of poisoning 

 as compared with control treated 

 with pure distilled water. 



