CLAYS OF ]S'EW YORK 



683 



Source 2 The manufacturing 

 a During molding 



1) By presence of sulfates in tlie water or coloring ma.tter 



2) By formation of sulfates during the drying 

 h During burning 



1) During water-smoking 



2) During firing 



Source 3 Environment of the bricks and buildings 



a Caused by the absorption of saline solutions from the soil of 



the place of storage 

 & Caused by the absorption of soluble salts from the soil on which 

 the building stands 



Yellow and green efflorescence 



1 Organic in character — caused by the action of vegetable 

 micro-organisms 



2 Inorganic in character — caused by soluble vanadinate salts 

 White efflorescence. Sulfates are seldom present in large quan- 

 tities, but according to Gerlach .1 to .05^ is sufficient to produce 

 an annoying white incrustation. This is prevented by rendering 

 the sulfate insoluble. The most effective way is by the addition of 

 some barium compound, specially the carbonate or chlorid. When 

 barium salts come in contact with sulfates, barium sulfate is formed, 

 a combination which is absolutely insoluble in water. This is 

 expressed by the following chemical reaction. 



CaS04+BaC03=CaC03+BaS04, 

 CaS04+BaC2=CalC)2+BaS04 



Thus it will be seen that in both cases we get insoluble compounds, 

 which are harmless. If the cost plays any part in the use of them, 

 it will be generally found that barium chlorid is the cheaper. 



Method of use. As carbonate of barium is insoluble in water, in 

 order to make it thoroughly and uniformly effective, it must be 

 mixed in with the clay very thoroughly, and in as finely divided a 

 condition as possible, because it will only act where it comes in 



