202 
DR. GLADSTONE ON CIRCUMSTANCES MODIFYING 
assumed on dilution a yellowish, and the meconate a pink hue. Numerical results, 
however, were obtained from the comparison of two mixtures, the one consisting of 
four equivalents of sulphocyanide of potassium and one of ferric chloride, the other 
of four equivalents of meconate of potash to one of the chloride of iron. They were 
made up to the same depth of colour, each occupying 200 grain measures. 
200 gr. rn. of the sulphocyanide equalled in colour 200 gr. m. of the meconate. 
400 gr. m. of the sulphocyanide equalled in colour 730 gr. m. of the meconate. 
720 gr. m. of the sulphocyanide equalled in colour 2460 gr. m. of the meconate. 
1440 gr. m. of the sulphocyanide equalled in colour 7540 gr. m. of the meconate. 
The disparity here is very great, and takes place at an increasing ratio. 
It seemed desirable to test, if possible, whether this diversity was due entirely to 
the sulphocyanide, or whether the meconate might not also be departing from the 
ratio of decrease in colour which mere dilution would cause.- For this purpose five 
solutions were taken of equal bulk and of the same depth of colour. They consisted 
respectively of meconate of iron, a mixture of ferric chloride and sulphocyanide of 
potassium, port wine and water, red ink, and infusion of cochineal. These solutions, 
though not identical in colour, were sufficiently near for the purpose. On repeated 
dilution of each with equal amounts of water, they all retained the same colour rela- 
tively, except the sulphocyanide, which became yellowish and much lighter. 
It may fairly be concluded then, without predicating anything as to the action of 
water on dry salts, that large quantities of water have no specific action on meconate 
of iron, but that in some way they affect the sulphocyanide. Is this a mere physical 
effect upon the particular colour; or does some change take place in the composition 
of the salt itself*? In order to test whether this action of water was influenced by 
the presence of other substances, red solutions of equal volume and equal depth of 
colour were prepared by the following admixtures : — ferric chloride with sulphocya- 
nide of potassium in large excess ; sulphocyanide of potassium with ferric chloride in 
large excess ; ferric nitrate with sulphocyanide of potassium ; the same salts with the 
addition of a large quantity of sulphate of potash ; sulphocyanide of potassium with 
ferric acetate ; ferrous and ferric sulphocyanide with sulphocyanide of lead ; and 
nearly pure sesquisulphocyanide of iron. On repeated dilution with equal amounts 
of water these all appeared to retain the same relative colour. 
It seems then, as far as this experiment can prove it, that the action of water, what- 
ever it be, is exerted equally upon red sulphocyanide of iron, with whatever other 
substance it may be mixed. This removes any doubt that might have rested from 
this cause on some of the original experiments with ferric sulphocyanide : and the 
fact that those experiments were always comparative, leaves little ground for any 
possible objeetion. 
An experiment was likewise tried in order to determine whether the presence of 
* See Note B. 
