52 URANIUM, ANTIMONY, CHROMIUM, &c. 



drous. The reader will observe, that 29*25 

 represents 26 atoms of water. Hence, if pro- 

 toxide of chromium weighs 4*5, the hydrate of it 

 is a componnd of 



1 atom protoxide of chromium 4.5 

 26 atoms water . . . 29'25 



33-75 



This hydrate appears perfectly dry j yet it con- 

 tains only T 2 jths of its weight of solid matter, 

 while Ifths consist of pure water. I am not 

 aware of any metallic hydrate that contains so 

 great a proportion of water, or so many atoms of 

 water as this one does. 

 Muriate of 337! m* a ins of this hydrate ( containing 45 



chromium. * ^ 



grains of protoxide of chromium) were dissolved 

 in muriatic acid, and the solution cautiously 

 evaporated in as low a temperature as possible 

 till the muriatic solution was reduced to the state 

 of a powder, apparently dry. It weighed 192*5 

 grains. From this experiment it is obvious, that 

 the atomic weight of protoxide of chromium is 

 4*5 ; for the salt was neutral. Hence, every atom 

 of the oxide must have combined with an atom 

 of muriatic acid. The quantity being 45, equiva- 

 lent to 10 atoms, must have united to 46*25 

 (equivalent to 10 atoms) of muriatic acid. The 

 remaining 101*25, wanting to complete the sum, 

 must be water, and it is equivalent to 90 atoms. 



