mony to the same general laws. The peculiar optical character of 

 certain salts of quinine was also taken advantage of for deter- 

 mining what changes took place among the compounds in solu- 

 tion. The amount of fluorescence exhibited by a solution of acid 

 sulphate of quinine was found to be affected by the admixture of a 

 chloride, bromide, or iodide according to the nature and the mass of 

 the salt added, and the addition of sulphuric, phosphoric, nitric and 

 other acids was found to produce a fluorescence in solutions either 

 of hydrochlorate of quinine, or of sulphate which had been rendered 

 non-fluorescent by hydrochloric acid. Similar results were obtained 

 with quinidine ; and somewhat analogous ones with the organic bases 

 contained in horse-chestnut bark, and in tincture of stramonium. 

 An experiment is also narrated showing that the same laws hold 

 good in respect to compound ethers as to salts having metallic 

 bases, alcohol being employed as the solvent. 



Beside the very diversified substances already mentioned in this 

 abstract, several others, such as lead, mercury, zinc, potash, soda, 

 baryta, lime, and ammonia, are shown by a more indirect proof to 

 enter into compounds which obey the same laws. Hence it is con- 

 cluded that what was observed in reference to the ferric salts holds 

 good very generally, if not universally. 



The bearing of certain other phenomena upon the question at 

 issue was also examined. The fact that precipitation, when it oc- 

 curs, gives rise to a perfect interchange of bases and acids, is equally 

 consistent with either Bergmann's or Berthollet's theory ; but not 

 so is the fact that two soluble salts cannot be mixed without the 

 occurrence of precipitation, if one of the products that may be formed 

 is an insoluble salt. The only recorded exception to this law, which 

 occurs with oxalate of iron in the presence of a salt of yttria, under 

 peculiar circumstances, was found on close examination to be in 

 perfect accordance with the principles laid down by Berthollet, 

 Besides the argument founded on this universal fact, several expe- 

 riments were devised for the purpose of proving that the complete 

 precipitation of an insoluble salt on the mixing of two soluble salts, 

 was due to the insoluble compound being removed at once out of the 

 field of action on the first distribution of the elements, thus neces- 

 sitating a redivision, and so on until no more of it could possibly be 

 formed. The phenomena attending volatilization have the same 



