74 DR. JAMES BOTTOMLEY ON COLORIMETRY. 



acid "would "be^ I took a solution containing i*6 gram in 

 500 cub. c. and divided it into two equal parts. To one I 

 added a little extremely dilute sulphuric acid. The colour 

 of tliis portion became decidedly deeper than that of the 

 other. I also tried what would be the effect of the addi- 

 tion of a little ammonia to a strong solution ; so I di-^dded 

 the solution containing 6*4 grms. in 500 cub. c. into two 

 equal portions. One I treated with ammonia : this I 

 thought a little lighter than the other ; but the difference 

 was very slight. This, however, Ave might expect ; for any 

 small change of intensity would be less noticeable in a 

 strong solution than in a dilute one. 



I now made some fresh experiments with chromate of 

 potashj a little ammonia being added to both columns. 

 The mean of four trials gave for the greater limit 3*35 ; 

 and the mean of four trials gave for the smaller limit 2* 18. 

 Hence the result will be as follows (standard solution o-8 

 gram in 500 cub. c. of water ; length of column 22'5): — 



A B C 



6'40o 2*77 6-498 



In this experiment I used the right eye. The theoretical 

 length is 2*8 1; and the above result is therefore a near 

 approximation. 



With the same solutions, on the following day (June 

 26th) the results were not so favourable; the mean of 

 eight trials gave 2*57 cm. as the length of the equivalent 

 column, the left eye being used in the determinations. 

 On the next day (June 27th) I repeated the experiments 

 with these solutions, using the right eye ; the mean of 

 four trials gave 2*3. To each solution I added 5 cub. c. 

 of ammonia, and repeated the experiment ; the mean of 

 four trials gave 2' 13 as the result. These differences of 

 results are probably due to some internal changes in the 

 coloured fluids i 



