44 DR. JAMES BOTTOMLEY S 



It seemed possible to me tliat a more satisfactory result 

 than this experiment had yielded might be obtained. The 

 excesses of ammonia used in the experiments were nearly 

 proportional to the quantities of sulphate of copper in so- 

 lution ; but if we regard water as an agent whose tendency 

 is to diminish the intensity of the colour, and ammonia as 

 an agent whose tendency is to restore the colour, it would 

 seem reasonable that the ammonia should be proportional 

 to the water. The difference of the excesses of ammonia 

 in the last two solutions was large, being 22 cub. c. I 

 prepared fresh solutions, one containing 4 cub. c. of the 

 copper-solution with 30 cub. c. of additional ammonia and 

 sufficient water to make 500 cub. c. The other solution 

 contained 15 cub. c. of the copper-solution with 30 cub. c. 

 of additional ammonia, and sufficient water to make 500 

 cub. c. The quantities of the copper-solution taken should 

 correspond to 1 600 and 6000 of copper-sulphate. To guard 

 against imperfect measurements from the burette, I also 

 weighed the solutions : the 4 cubic centimetres weighed 

 3-9854 grams; and the 15 cubic centimetres weighed 14*99 

 grams. The ratio of the volumes is 375, and the ratio of 

 the weights is 3761; so that the error of measurement 

 would be but small. 



With disks outside, the results of experiments were as 

 foUows; standard solution 1600 in 500 cub. c. of water, 

 length of column 21-2 : — 



ABO 



6000 6 5653 



The number under B was the result of eight trials ; also 

 the standard solution was on the left hand. With the 

 standard solution on the right the results were : — 



A B 



6000 5'4 6283 



