CHEMICAL COMPOSITION OF MINERALS. 339 



Tungsten (Wolfram), W, 1150 



Tungstic acid, W, 



1450 



Uranium, U, 



750 



Protoxyd of U., ft, 



850 



Peroxyd of U., g, 



1800 



Vanadium, V, 



856-9 



Yttrium, Y, 



402-5 



Yttria, Y, 



5025 (O, 19-9) 



Zinc, Zn, 



406-6 



Oxyd of Zinc, Zn, 



506-6 (O, 19-14) 



Zirconium, Zr, 



419-1 



Zirconia, Sar, 



11395 (O, 26-3) 



By atomic weights is understood the combining prop.rtions 

 of the elements. For example, when iron and oxygen com- 

 bine, they unite in the proportions of 350 parts by weight of 

 iron to 100 of oxygen, or in some simple multiple of these 

 numbers. The protoxyd contains one part or atom of each, and 

 has therefore the atomic weight 450 ; the peroxyd (more pre- 

 cisely sesquioxyd) contains 2 of iron (2-X 350=100) to 3 of 

 oxygen (3X100:=300), and therefore has the atomic weighs 

 1000 (100+300=: 1000). To ascertain the per-centage of 

 oxygen in this oxyd, we have 300 of oxygen in 1000 parts; 

 hence the ratio, — 1000 are to 300 as 100 to the number of 

 parts in 100; therefore dividing 300X100 by 1000 give 

 the oxygen per-centage. Hence too if we multiply the per- 

 centage of oxygen by the atomic weight of the oxyd, we ob- 

 tain as a result, after dividing by 100, the oxygen amount in 

 the compound. For alumina, 46'1X642-5-~100=300, the 

 amount of oxygen ; and in this way the correctness of the 

 oxygen per-centage may be verified. 



The mode of deducing chemical formulas may be illustra* 

 ted by two or three examples. 



1. We have an analysis of Red Silver Ore as follows : 

 Silver 59*02, antimony 23-49, and sulphur 11*49 per cent 

 It is desired to ascertain the relative number of atoms of 

 each element in the compound. This number must depend 

 on the weights of the atoms, as compared with the quantity 

 of each, for the less the weight, the greater the number of' 

 atoms. The rule consequently is, — Divide the per-centage of 

 each element by the atomic weight of the same ; as, 5*02 by 



