CHEMICAL COMPOSITION OF MINERALS. 



77 



Lithium 



Magnesium 



Manganese 



Mercury 



Molybdenum 



Nickel 



Ni trogen 



Osmium 



Oxygen 



Palladium 



Phospho /us 



Platinum 



Potassium 



Rhodium 



Rubidium 



Ruthenium 



Selenium 



Li 



7 



Silver 



Mg 



24 



Silicon 



Mn 



55 



! Sodium 



Hg 



200 



Strontium 



Mo 



96 



1 Sulphur 



Ni 



58-8 



Tantalum 



N 



14 



Tellurium 



Os 



199-2 



| Thallium 







16 



! Thorium 



Pd 



106-6 



Tin 



P 



31 



Titanium 



Pt 



197-6 



Tungsten 



K 



39-1 



Uranium 



Ro 



104-4 



Vanadium 



Rb 



85-4 



Yttrium 



Ru 



104 4 



Zinc 



Se 



79-4 



Zirconium 



Ag 



Si 



Na 



Sr 



S 



Ta 



Te 



Tl 



Th 



Sn 



Ti 



W 



U 



V 



Y - 



Zn 



Zr 



108 



28 



23 



87-6 



32 

 182 

 128 

 204 

 235 

 118 



50 

 184 

 240 



51-2 



92 



65-2 



89-6 



The combining weights indicate the proportions in which the 

 elements combine. Thus, assuming hydrogen, the lightest of 

 the elemeuts, to be 1, or the unit of the series, the combining 

 weight of oxygen is 16 ; of iron, §6 ; of magnesium, 24 ; of 

 Bulphur, 32 ; and so on. When hydrogen and oxygen combine 

 it is in the ratio of 2 pounds of hydrogen, or else 1 pound of 

 hydrogen, to 16 pounds of oxygen, and two different compounds 

 thus result. When oxygen and magnesium combine it is in the 

 ratio of 16 pounds of oxygen to 24 of magnesium. Oxygen and 

 iron combine in the ratio of 16 of oxygen to 56 of iron ; or of 24 

 of oxygen (1£ times 1 6) to 56. Sulphur and oxygen combine in 

 the ratio of 32 of oxygen to 32 of sulphur; or of 48 to 32 of 

 sulphur. The combining weights are often called the atomic 

 weights. 



The following is the manner of using the symbols : For the 

 compound consisting of hydrogen and oxygen in the ratio of 2 

 to 16, the chemical symbol is H 2 G, meaning 2 of hydrogen to 1 

 of oxygen. (This compound is water.) For the compound of 

 oxygen and magnesium just referred to, the symbol is MgO; 

 for the two compounds of oxygen and iron, FeO, protoxide of 

 iron; Fe 4 3 , sesquioxide of iron, the ratio of 1 to 1^ being ex- 

 pressed by 2 to 3 ; for the two compounds of sulphur and oxy- 

 gen, S0 2 and £0 3 . 



Some of the elements so closely resemble one another that 

 their similar compounds are closely alike in crystallization and 

 other qualities, and they are therefore said to be isomorphous. 



This is true of iron, magnesium, calcium, and two or three 

 other related elements. In one group of compounds of these 

 bases, the carbonates, the crystalline form for each is rhombohe- 



