J64 ATTRACTION. 



other base, and are therefore called chemical equivalents, and the 

 same is true of the bases, in relation to the acids. 



Wenzel, a German chemist, proved, in a work published in 1777, 

 that two neutral salts that decompose each other, still preserve their 

 neutrality ; neither acid nor base being in excess,* and Richter, of 

 Berlin, illustrated this truth more fully in 1792. This could not 

 have been true, had not the relations of acids and bases been con- 

 stant, as stated in the two last propositions. Thus, in sulphate of 

 potassa, the acid is in the proportion 40, and the alkali 48=88, and 

 in nitrate of baryta the acid is 54, and the earth 78 = 132. Now 

 when these salts are, by double decomposition, converted into sul- 

 phate of baryta, and nitrate of potassa, the 54 parts of nitric acid in 

 the nitrate of baryta will saturate and be saturated by the 48 parts of 

 potassa in the sulphate of potassa, making 102 of the new salt, the 

 nitrate of potassa, and the 40 of sulphuric acid in the sulphate of 

 potassa, will saturate and be saturated by the 78 of baryta, in the 

 nitrate of baryta, making 118 of the sulphate of baryta. The facts 

 may be concisely expressed thus. 



Before decomposition. 



Sulphuric acid 40 -f potassa 48= 88 sulphate of potassa. 

 Nitric acid 54 -j- baryta 78 = 132 nitrate of buryta. 



"220 

 Jlfter decomposition. 



Sulphuric acid 40 -f baryta 78 = 118 sulphate of baryta. 

 Nitric acid 54-}- potassa 48 = 102 nitrate of potassa. 



220~ 



The sum of the constituents being the same after decomposition 

 as before, it is obvious there can be no excess of either. 



Thus then, hydrogen being unity, we are to infer that 40, or a 

 multiple of it by a whole number, will always express the combining 

 power of sulphuric acid, and so of other principles. 



(W.) CHEMICAL EQUIVALENTS ARE THOSE DEFINITE QUANTI- 

 TIES OF PARTICULAR SUBSTANCES THAT SATURATE DEFINITE QUAN- 

 TITIES OF OTHER SUBSTANCES. 



This is only expressing in the form of a proposition, what has been 

 already stated ; namely, that a unit being chosen, it becomes possible 

 to express the combining power of all bodies, both simple and com- 

 pound, by numbers. Thus, if the combining power of hydrogen be 



* For an interesting account of the progress of the doctrine of definite proportions 

 see the introduction to Dr. Thomson's First Principles of Chemistry. 



