104 



SALTS OF SOD*. 



fibrous layer an inch thick beneath the soil, and several hun 

 dred tons are collected annually. At a lake in Maracaibo 

 "8 miles from Merido, it is very abundant. 

 , Uses. Carbonate of soda is used extensively in the manu- 

 facture of soap. The powders put up for making soda water 

 consist of this salt and tartaric acid. On mixing the two, 

 the tartaric acid unites with the soda and the carbonic acid 

 of the carbonate of soda escapes as a gas producing the effer- 

 vescence. In Mexico, this salt (or the sesquicarbonate, 

 trona) occurs in such abundance over extensive districts that 

 it is employed as a flux in smelting ores of silver, especially 

 the chlorid of silver which is a common ore. 



C OMMON SALT. 



" "^^ 



Monometric. In cubes v(fig 1) and its secondaries, as the 

 following. Sometimes crystals have the shape of a shallow 

 1 2 3 4 



p p 



cup like figure 4, and are called hopper shaped crystals. They 

 I w T ere formed floating ; the cun receiving its enlargement at 

 the margin, this being the part which lay at die surface of 

 the brine where* evaporation wfss o-oing on. J Common salt 

 is usually white or grayish, but sometimes presents rose red. 

 yellow and amethystine tints. JRf =ti. Gr=2'257. Taste 

 saline. 



Composition : chlorine 60*7, solium &9'li. Crackles or 

 decrepitates when heated. 



Dif. Distinguished by its taste solubility, and blowpipe 

 characters. 



Obs. Salt is usually associated with jryosum, and clavs or 

 sandstone. It occurs in extensive beds in Spain, in the Pyre- 

 nees, in the valley of Cardona and elsewhere, forming hills 

 300 to 400 feet high ; in Poland at Wieliczka ; at Hail in the 

 Tyrol, and along a range through Reichenthal in Bavaria. 



For what is it used 1 What happens when tartaric r^H np<i ^a^bon- 

 ate of soda are mixed 1 What are the forms of crystals of common 

 salt? Of what does It consist ? Where are some of the mret remarkable 

 deposits of rock salt ? 



