COMBINING PROPORTIONS. 117 



177 nitrogen in analogous compounds. The equivalent of car- 

 bon may be deduced from the known equivalent of its com- 

 pound, carbonic acid. But the equivalents of boron and silicon 

 cannot be fixed upon with the same certainty, owing to the 

 doubt which hangs over the equivalents of boracic and silicic 

 acids. 



Of the facts which involve the principle of combination in 

 definite and equivalent proportions the last mentioned appears 

 to have been the first observed and explained. Wenzel of Frey- 

 berg in Saxony so far back as 1777 made an analysis of a great 

 variety of salts with surprising accuracy, which enabled him to 

 perceive that the neutrality which is observed after the mutual 

 decomposition of neutral salts depends upon this, that the quan- 

 tities of different acids which saturate an equal weight of one 

 base will also saturate equal weights of any other base. 



Richter of Berlin confirmed and extended the observations of 

 Wenzel, attaching proportional numbers to the acids and bases, 

 and remarking for the first time that the neutrality does not 

 change during the precipitation of metals by each other, and 

 also that the proportion of oxygen in the equivalents of bases 

 is the same in all, and may be represented by 1 00 parts. But 

 the first foundations of a complete system of equivalents, em- 

 bracing both simple bodies and their compounds were laid by 

 Dalton, at the same time that he announced his atomic theory.* 

 The observation that the equivalent of a compound body is the 

 sum of the equivalents of its constituents, and the discovery of 

 combination in multiple proportions are peculiarly his. Dr. 

 Wollaston afterwards adapted the more important equivalents 

 to the common sliding rule of Gunter, by means of which, pro- 

 portions can be observed without the trouble of calculation. 

 This instrument, which is known under the name of the scale of 

 chemical equivalents, contributed largely to the diffusion of the 

 knowledge of the proportional numbers, but is not itself of 

 much practical value. 



The numerical accuracy of the equivalents assigned to bodies, 

 depends entirely upon the exactness of the chemical analyses 

 from which they are deduced. The generally received series of 

 numbers, which is adopted in this work, was drawn up by 

 Berzelius from data supplied in a great measure by himself* 



* New system of Chemical Philosophy, 1807. 



