Q 



CHEMICAL SCIENCE. 22; 



when they remain free to act and react on one another. Supposing 

 they all remain in solution, the requisite is fulfilled ; but how are we to 

 know what has then taken place ? Maiaguti thought to obtain an indica- 

 tion of this by mixing the aqueous solutions of two salts, one of which is 

 soluble in alcohol, and the other is insoluble, and then pouring them into 

 very strong alcohol, and analyzing the salts immediately thrown down. 

 1] is results are tabulated; they are valuable, but to some extent open to 

 objection, on account of the disturbing influence of the alcohol. The 

 lecturer then proceeded to describe his own endeavors to arrive at a knowl- 

 edge of the intimate constitution of a mixture of salts in solution by 

 observing their physical properties, especially color. If solutions of one 

 equivalent of nitrate of iron, and a triple equivalent of sulphocyanide of 

 potassium, be mixed, a blood-reel color results, owing to the formation of 

 sulphocyanide of the sesquioxide of iron. The question arises, Has all 

 the iron left the nitric acid to unite itself with the sulphocyanogen ? It 

 has not ; for, on the addition of equivalent after equivalent of sulpho- 

 cyanide of potassium, a deeper red is constantly obtained. The arrange- 

 ment by which this deepening of color was quantitatively determined was 

 explained, and imitated on the lecture table. The result was, that, even up 

 to 375 equivalents, a regular increase was observed to take place more 

 rapidly at first than afterwards, which was exhibited to the eye by the 

 results being projected as a curve. Again : as, in the mixture of equal 

 equivalents of the two salts, some iron still remains in combination with 

 the nitric acid, a portion of the potassium must still remain united to the 

 sulphocyanogen. Accordingly, the addition of more iron salt also gives a 

 deeper color. The curve expressing the results of this experiment was a 

 regular continuation of the curve formerly mentioned ; and neither of 

 them exhibited any of those sudden transitions which the experiments of 

 Eunsen and Debus present. Various experiments were then performed, 

 showing the alteration in the resulting color upon any change of any of 

 the elements in the primary experiment ; for instance, the substitution of 

 other acids for the nitric acid, or of other bases for the potash. On the 

 addition of a colorless salt to a colored one, there results a diminution of 

 the color greater than the mere dilution would have produced, as was 

 exemplified in the cases of the red sulphocyanide of iron mixed with 

 sulphate of potash, and of the scarlet bromide of gold mixed with chloride 

 of potassium. The lecturer accordingly drew the conclusion, that, when 

 two salts mix without precipitation or volatilization, the acids and bases 

 frequently, if not universally, arrange themselves according to some defi- 

 nite proportion, and that this depends on the relative quantity of the 

 two salts, as well as upon the proper affinities of the substances composing 

 them. He was unable then to enter upon the influence of heat, or of 

 dilution in certain cases, or to add any remarks connected with double 

 salts or with other metals, or upon certain practical applications of these 

 views in chemical and physiological science. The fact that we very fre- 

 quently find the double decomposition of a salt to be complete, the whole 



