300 



of the influence both of the nature and of the mass of every sub- 

 stance present at the same time in the mixture ; the purple and the 

 red comenamate afforded similar results ; while the red bromide 

 (not the oxybromide), though somewhat indistinct in its testimony, 

 corroborated to a certain extent the preceding observations. 



Experiments were performed with a view to determine what effect 

 the mass of water might have on the salts operated upon ; its influence 

 in reducing the colour of the ferric sulphocyanide was found to be 

 very great, but the nature of it could not be exactly determined. 

 As however it was uniform in its action in whatever manner the 

 sulphocyanide had been produced, it could not affect the results of 

 the preceding experiments. Water did not appear to act in any 

 similar manner upon the other ferric salts. 



From the mass of quantitative observations made during the inves- 

 tigation, it was possible to deduce not only the order of affinity of 

 the various acids for sesquioxide of iron as compared with potash, 

 but also to assign approximative numbers. Doubt may rest on the 

 position of some terms in the series, but hydrosulphocyanic acid 

 certainly had the least affinity for ferric oxide in comparison with 

 potash : it was represented by unity : the other acids followed in 

 the order nitric, 4 ; hydrochloric, 5 ; sulphuric, 7 ; gallic, 10 ; 

 pyromeconic ; meconic ; acetic, 20 ; hydrobromic ; comenamic ; 

 citric, 100; hydroferrocyanic, 170. 



Other coloured salts were submitted to a more cursory investiga- 

 tion. The scarlet bromide of gold when treated with an alkaline 

 chloride gave a striking instance of the effect of mass in gradually 

 overcoming a strong affinity. The intensely red iodide of platinum 

 afforded results which, though somewhat obscure, were not opposed 

 in their testimony. So did the blue sulphate of copper when treated 

 with different chlorides. The " manganoso-manganic oxide" dis- 

 solves in sulphuric or phosphoric acid of a red, and in other acids of 

 a deep brown colour ; and it was found that hydrochloric acid was 

 capable of changing the colour of the sulphate according to its mass, 

 while on the other hand sulphuric or phosphoric acid altered in like 

 manner the tint of the chloride. Somewhat similar results were ob- 

 tained by means of the green chloride and the purple fluoride of mo- 

 lybdenum ; and the blue solution that forms when gallic acid is 

 brought in contact with both the oxides of iron at once, bore testi- 



