TASTE AND ODOR. 75 



4. Alkaline — taste of soda. 



5. Cooling — taste of saltpetre. 



6. Hitter — taste of epsom salts. 



7. /Sour — taste of sulphuric acid. 



Odor is not given off by minerals in the dry, unchanged 

 Btate, except in the case of a few gases and soluble minerals. 

 By friction, moistening with the breath, the action of acids and 

 the blowpipe, odors are sometimes obtained, which are thus 

 designated : 



1. Alliaceous — the odor of garlic. It is the odor of burning 

 arsenic, and is obtained by friction, and more distinctly by 

 means of the blowpipe, from several arsenical ores. 



2. Horse-radish odor — the odor of decaying horse-radish. It 

 is the odor of burning selenium, and is strongly perceived when 

 ores of this metal are heated before the blowpipe. 



3. Sulphureous — odor of burning sulphur. Friction will 

 elicit this odor from pyrites, and heat from many sulphides. 



4. Fetid — the odor of rotten eggs or sulphuretted hydrogen. 

 It is elicited by friction from some varieties of quartz and lime- 

 stone. 



5. Argillaceous — the odor of moistened clay. It is giren ofl 

 by serpentine and some allied minerals when breathed upon. 

 Other?, as pyrargillite, afford it when heated. 



