224 Mr. Brande on the Analysis 



dry salt to a red heat in a small platinum capsule ; the maig- 

 nesia, if any were present, will remain ; if not there will be no 

 residue, for the oxalic acid and muriate of ammonia will be 

 destroyed and volatilized. 



100 parts of oxalate of lime indicate 77 of carbonate of lime. 



100 parts of red oxide of iron indicate 90 of black oxide, or 

 143 of carbonate of iron. 



When carbonic acid holds iron in solution, the metal is in 

 the state of protoxide, and if air be excluded it requires long 

 boiling to decompose it ; for the same reason, if the water be 

 exposed, under the exhausted receiver of the air-pump, it does 

 not readily become brown, as is the case when it is exposed to 

 air ; a drop or two of nitric acid facilitates the deposition of 

 the red oxide. 



100 parts of ptire magnesia ai'e equivalent to 213 of carbo- 

 nate of magnesia. 



/ 10. The dry residue B, is to be digested in six or eight parts 

 of boiling alcohol, specific gravity 0.817, which will take up 

 muriate of magnesia, and in some rare cases (where no sulphates 

 are present) muriate of lime. Filter off the alcoholic solution, 

 and wash the residue C with a little fresh alcohol, which add 

 to the former, and evaporate to dryness D. The dry mass D, 

 exposed for some time to a heat of 500°., is generally pure 

 muriate of magnesia ; if it contain muriate of lime, the latter 

 earth may be separated by solution of oxalic acid, in the state 

 of oxalate of lime. 



I have found it, in some cases, convenient to convert the 

 muriates of lime and magnesia into sulphates, by pouring upon 

 them excess of sulphuric acid, evaporating to dryness, and 

 heating the dry mass red hot. The sulphate of magnesia may 

 then be almost completely separated from the sulphate of lime, 

 by a small quantity of cold water ; or a saturated solution of 

 sulphate of lime may be used, which takes up the sulphate of 

 magnesia, and, of course, leaves the sulphate of lime. 



The alcohol will also take up a very minute portion of sea- 

 salt, which, however, is too small to require estimation. 



11. The residue C, insoluble in alcohol, may contain sea-salt, 



