328 SALTS SULPHATES. 



the plaster is cast in moulds, or figured on the spot to which it is ap- 

 plied. 



Sometimes used to adulterate flour. 



Discovered by weighing a given measure, by grittiness be- 

 tween the teeth, by alcohol throwing it down from water that has been 

 boiled on the flour, by the tests for lime and sulphuric acid, by burn- 

 ing the flour in the open air, and examining the residuum and by 

 forming heavy bread. 



Besides the uses of this salt for statues, &c. it is employed in -cer- 

 tain proportions with common lime plaster, to give it firmness and 

 beauty, and such walls will bear washing and cleaning with soap. It 

 is largely and most advantageously employed in agriculture as a 

 manure, on sandy soils and grass lands. * It is extensively used in 

 Switzerland, but very little, if at all, in Great Britain. It need not 

 be burned, but merely pulverized. At Paris, and in Minorca, it is 

 employed in building houses. Abundant in Nova Scotia, and in many 

 of the Western American States ; a very beautiful transparent va- 

 riety is found at Lockport, and the compact variety exists extensive- 

 ly in other places in the state of New York. 



SULPHATE OF BARYTA. 



1. NAME, &c, 



(a.) The native mineral formerly called ponderous spar ; its sp. 

 gr. being from 4.3 to 4.7. 



(b.) Its composition first ascertained by Ghan. 



2. NATURAL HISTORY. 



(a.) Found native, in almost every country, particularly in metal- 

 lic veins, of which it often forms the gangue ; it is frequently amorphous, 

 compact or granular, and of a pure white, or red, brown, yellow, &c. 



(b.) Often crystallized, or fibrous, translucent, transparent or 

 opake.f 



3. PREPARATION. By mingling barytic water or any soluble salt 

 of baryta, with sulphuric acid or any soluble salt containing it ; there 

 is an immediate dense precipitate. 



4. PROPERTIES. 



(a.) By heat, the foliated natural sulphate decrepitates, and melts 

 under the blowpipe, at about 35, Wedg. 



(b.) Tasteless and inodorous, insoluble in water ; or requires ac- 

 cording to Kirwan, 43,000 parts of water. 



* The popular opinion that it will not answer near the sea, appears to be erroneous, 

 as was proved by the late Mr. M. Rogers, at his place, near Stamford, Conn, 

 where, as I heard him say, it produced the most striking effects on land washed by 

 the salt water. Dr. Black says its effects last two years, and he asserts, contrary to 

 our impressions in this country, that it is most efficacious on strong and rich lands. 



t Found sometimes in sandstone, in Scotland ; rarely, in the same country, in 

 granite, in the place of the felspar ; occasionally in the interior of Scotch agates, and 

 in the ludus helmontii, of England. 



