2 44 , ON A NATURAL SYSTEM 



which, according as. the faline mutter is either 

 the fame or dillbrcnt in each, generate triple or 

 quadruple compounds. 



LXXII. Doubtful Genera of Salts. 



IN tlie clafs of falts it often happens, that 

 iome principles are never found in a lingle and 

 independent llate, hut united always with others. 

 Such are, for example, the nitrous, the muria- 

 tic, and arfenical acid, it may be doubted, 

 therefore, whether thefe fubilances are to be 

 COiiiiderctl under their iimpic genera. As, how- 

 ever, it does not feeiii improbable, that they 

 were once free and uncombined, we are hardly 

 authorized to exclude them ; though it may be t 

 at the fume time, obfcrvcd, that they have ne- 

 ver yet been found otherwiic than inthis itate of 

 combination. At all events, the iaveiligation 

 of iiinple Jubilance* \\ili throw light, upon the 

 fcveral compoJhion:;, 



LXXII i. Genera of Earths. 



SOME genera of earths have hitherto refilled 



all attempt* to reduce them into limpler princi- 

 ples; while other*, by a proper analyiis, have 

 difcovcrcd two or more. The former arc called 

 primitive, the latter, dtrivati vc earths. 



* 



JLXXIV. 



