COMBINATION. 339 



pounds of elementary bodies. Sulphifes are more complicated unions of the 

 compounds. Sulphates are the salts formed by the union of sulphuric acid 

 with bases. Sulphides or sulphurets are compounds in which sulphur forms 

 the electro- negative element, and sulphites are salts formed by the union of 

 sulphur^j acids with bases, or by their action upon them. 



The symbolical nomenclature of the chemist is worse than Greek to 

 the uninitiated. We frequently see in so-called popular chemical books a 

 number of hieroglyphics and combinations of letters with figures very difficult 



d 

 ^ 



Fig. 322. Combinations of elements. 



to decipher, much less to interpret. These symbols take the place of the 

 names of the chemical compounds. Thus water is made up of oxygen and 

 hydrogen in certain proportions ; that is, two of hydrogen to one of oxygen. 

 The symbolic reading is simple, H 2 O, = the oxide of hydrogen. Potassium 

 again mingles with oxygen. Potassium is K in our list ; KO is oxide of 

 potassium (potash). Let us look into this a little closer. 



The union of one particle of a simple body with a particle of another 

 simple body can be easily understood ; but, as we have seen, it is possible to 

 have substances consisting of four or five different particles, though the 

 greater number of chemical combinations consist of two or three dissimilar 

 ones. In the diagram (fig. 322) we have some possible combinations. 



In these combinations we may have one particle of a in combination 

 with one, two, three, four, or five of , and many particles of a can unite with 

 various molecules of b. Suppose we have oxygen and sulphur compounds 

 as follows : 



Thus there are three different compounds of these two elements 

 SO, SO,>, SO 3 (without water). 



A compound body may combine with another compound body, and 



(0 



sYo 



^^ ^_^ 



Fig. 323. (i) Hydrosulphurous Acid. (2) Sulphurous Acid. 



this makes a complicated compound. Suppose we have a mixture of sulphuric 

 acid and potash. We have a sulphate of potassium (KsSO 4 ) and combinations 

 of these combinations may likewise be formed. We must read these symbols 

 by the light of the combining weights given in the table, and then we shall find 

 the weight of oxygen or other elements in combination. Thus when we see 

 a certain symbol (Hg.S for instance), we understand that they form a com- 

 pound including so many parts of mercury and so many of sulphur, which is 

 known as vermilion. Hg.O is oxide of mercury, and by reference to the 

 table of Atomic Weights, we find mercury is Hg., and its combining weight is 



