398 Alfred J. Ewart: 



In the same way the presence of a sulphate in the cells will 

 protect them against the toxic action of barium. Thus pre- 

 pared apples floated for two days on a 1 per 10,000 solution 

 of potassium sulphate and then on a 1 per 10,000 solution of 

 barium chlorate for five days, showed only doubtful or no signs 

 of poisoning, whereas after one week on 1 per 10,000 of potas- 

 sium sulphate slight, and after one week on 1 per 10,000 of 

 barium chlorate distinct, signs of poisoning were produced. 



Even where no precipitation takes place, two salts jointly may 

 not exercise any greater toxic action than either salt singly when 

 in considerable dilution, although the total concentration is 

 doubled with the mixtures of the two salts. This is well shown 

 by the following results: — 



Prepared Rome Beauties. — One week on solution, and 

 examined after one week. 



Barium chlorate, 1 per 10,000. From superficial browning to 

 pits 1 mm. deep. 



Barium chlorate 1 per 10,000, and potassium chlorate 1 per 

 10,000. From superficial browning to pits 1 mm. deep. 



Potassium chlorate, 1 per 10,000. Superficial browning to pits 

 0.5 mm. deep. 



Potassium chlorate 1 per 10,000, and magnesium sulphate 1 

 per 10,000. Superficial browning to pits 0.5 mm. deep. 



The addition of a poisonous anion to a dilute toxic solution 

 may even decrease the poisonous action of the mixture if it 

 diminishes the amount of dissociation of a highly toxic kation. 

 This is probably the explanation of the following results in which 

 the addition of citric acid diminished the toxicity of copper 

 sulphate, and the addition of sulphuric acid to copper sulphate 

 produced no increase, but if anything a slight decrease of toxi- 

 city. The materials and times were as in the experiments 

 abovei. 



Copper sulphate, 1 per 1,000,000. Pits 1-2 mm. deep. 



Copper sulphate 1 per 1,000,000, and sulphuric acid 1 per 

 2,000,000. Pits mostly just over 1 mm. deep. 



1 Mr. Rivett informs me that the decrease in the concentration of copper ions would 

 be much greater in the presence of citric acid than in the presence of an equivalent amount 

 of sulphuric acid. The decrease is in fact so great that no copper hydroxide can be precip. 

 itated bv caustic alkali. 



