CHEMISTRY OF THE EIGHTEENTH CENTURY. 379 



quantities of the salts present the inference may be made as to what 

 proportions of the two acids are equivalent to each other, and what 

 quantity of one base replaces a given quantity of the other. 



The law of equivalent proportions as regards acids and bases was 

 placed in a still clearer light some years afterwards by J. B. RICHTER, 

 who in 1 794 published a work in three volumes on the art of estimating 

 chemical elements, and in other publications from 1796 to 1798 de- 

 veloped still further the doctrine of equivalency. Richter found the 

 quantities of the several bases which were required to separately neu- 

 tralize a fixed quantity of each acid. He took, for instance, 1,000 

 grains of sulphuric acid, and found the quantity of potash required to 

 neutralize it. Then he found the quantity of soda required to neu- 

 tralize another 1,000 grains of sulphuric acid, and so on with other 

 bases. The like determinations were then made with some fixed 

 quantity of nitric acid. Now, the proportions which subsisted between 

 the quantities of the several bases required for the one acid were found 

 to be identical with those required for the other acid. It was possible 

 to express by numbers the quantities of each base which are equivalent 

 to each other in their acid-saturating powers. Thus, 74 parts by 

 weight of lime were found to be equivalent to 80 of soda, or to 1 1 2 of 

 potash, and so on. 



It will be readily understood that the law of equivalency in bases 

 and acids necessarily implies the law of definite proportions in the 

 composition of salts. The consequences deducible from the facts 

 established by Wenzel and Richter had, however, to wait for the recog- 

 nition of their importance ; and their theoretical interpretation came 

 from an illustrious Englishman, whose labours also made an important 

 addition to the facts themselves. This was John Dalton of Man- 

 chester. 



The labours of CLAUDE Louis BERTHOLLET (1748 1822), the emi- 

 nent French chemist referred to on the preceding page, call for special 

 notice, as they powerfully contributed to the progress of chemical 

 science and its applications to the arts, Berthollet was a native of 

 Annecy, in Savoy, and after having graduated in medicine at the Uni- 

 versity of Turin, he came to Paris, where he obtained a lucrative appoint- 

 ment as physician. His tastes, however, determined his attention to 

 the study of chemistry, and he was one of the first to adopt the new 

 views propounded by Lavoisier, taking part, as we have already seen, 

 in the establishing of the modern nomenclature of the science. Ber- 

 thollet's talents obtained for him the most distinguished professorial 

 and official appointments in connection with science and art, while 

 he was remarkable for his modesty of character and unostentatious 

 manners. His investigations included an extension of the researches 

 on ammonia which Priestley had begun, and an examination of the 

 nature and properties of " oxy-muriatic acid," or chlorine as we now call 

 it. The useful salt called chlorate of potash was one of his discoveries* 



