222 ANNUAL OP SCIENTIFIC DISCOVERY. 



with ethyl, we had additional and striking evidence of the same law ; for 

 the affinities of arsenic, tin, and antimony, were, in these compounds, 

 exalted in a most remarkable manner by the approximation of similarly 

 electrified atoms. These examples seemed to prove clearly the great 

 influence of the electrical character of elements upon the chemical proper- 

 ties of their compounds ; but further study of the subject also revealed 

 the paramount influence of molecular structure, which modified and con- 

 trolled the effects of electrical character, and limited all affinity, however 

 heightened by electric induction. 



ON CHEMICAL AFFINITY AMONG SUBSTANCES IN SOLUTION. 



The following is an abstract of a paper read before the Royal Institu- 

 tion by Dr. J. H. Gladstone : 



Attention was first directed to the doctrine of Bergmann, that when a 

 decomposition takes place by means of the greater electro attraction of a 

 third body, that decomposition is complete. In opposition to this, Ber- 

 thollet contended, that in all such cases of composition, or decomposition, 

 there takes place a partition of the base, or subject of the combination, 

 between the two bodies whose actions are opposed ; and that the propor- 

 tions of this partition are determined, not solely by the difference of energy 

 in the affinities, but also by the difference of the quantities of the bodies 

 by their physical condition and by that of the combination capable of 

 being generated. Several experiments were made to show how easily 

 elective affinity was affected by circumstances. Thus ammonia will dis- 

 place alumina from a solution of the sulphate ; but, on the other hand, 

 alumina will displace ammonia when heated with the solid sulphate of 

 that volatile base ; whilst if solutions of chloride of aluminum and sul- 

 phate of ammonia be mixed and evaporated, crystals of the double 

 sulphate ammonia alum will appear. So great is the influence exerted by 

 these various circumstances that some have doubted whether there be a 

 true elective affinity ; but, after making every allowance for known causes, 

 there is still a residuary phenomena to which that name is the most appro- 

 priate. Allowing then, with Bergmann, that relative degrees of affinity 

 exist, the question arises, Is Berthollet's law also correct r It is difficult to 

 arrive at a satisfactory answer, since it is almost impossible to eliminate 

 other influences. Several reactions, however, were mentioned as tending 

 to show that there is some truth in the law : for instance, the solution of 

 gold in hydrochloric acid upon the addition of nitrate of potash. The 

 experiments of Bunsen on mixtures of carbonic oxide and hydrogen, 

 exploded with a quantity of oxygen insufficient for complete combustion ; 

 and those of Debus, on the precipitation of mixed hydrates of lime and 

 baryta by carbonic acid, were explained ; as also the remarkable fact, 

 noticed by both, that the resulting products were always in certain atomic 

 proportions to one another. But in both these cases, the first products of 

 the chemical action are removed at once from the field : it is quite another 



