102 SALTS OF SODA. 



exportation. It is there used for making a cooling mixture , 

 an ounce of powdered niter in five ounces of water reduces 

 the temperature 15 F. 



Spain and Egypt also afford large quantities of niter for 

 commerce. This salt forms on the ground in the hot weather 

 succeeding copious rains, and appears in silky tufts or efflo- 

 rescences ; these are brushed up by a kind of broom, lixiviated, 

 and after settling, evaporated and crystallized. In France, 

 Germany, Sweden, Hungary and other countries, there are 

 artificial arrangements called nitriaries or niter-beds, from 

 which niter is obtained by the decomposition mostly of the 

 nitrates of lime aud magnesia which form in these beds. 

 Refuse animal and vegetable matter putrified in contact with 

 calcareous soils produces nitrate of lime, which affords the 

 niter by reaction with carbonate of potash. Old plaster 

 lixiviated affords about 5 per cent. This last method is much 

 used in France. 



Chlorid of potassium, or sylvine, has been observed with salt at 

 Sakzburg. 



3. SODA. 



The following salts of soda are all more or less soluble : 

 they are in general distinguished by giving a deep yellow 

 light before the blowpipe. Hardness below 3 ; specific 

 gravity below 2*9. 



glauber salt. — Sulphate of Soda. 



Monoclinic. In oblique rhombic prisms. Occurs in 

 efflorescent crusts of a white or yellowish-white color ; also 

 in many mineral waters. Taste cool, then feebly saline and 

 bitter. Composition, soda 19*3, sul. acid 24'8. water 55*9. 



Dif. It is distinguished from Epsom salt, for which it is 

 sometimes mistaken, by its coarse crystals, and the yellow 

 color it gives to the blowpipe flame. 



Uses. It is used in medicine, and is known by the famil 

 iar name of "salts." 



Obs. On Hawaii, one of the Sandwich Islands, in a care 

 at Kailua, glauber salt is abundant, and is constantly forming. 

 It is obtained by the natives and used as medicine. Glauber 



What is a nitriary ? What effect is produced on the blowpipe flame 

 by soda ? What is its composition ? How is it distinguished from 

 Epsom salt 1 Where does Glauber salt occur native ? 



