226 Mr. Brands on the Analysis 



illustrate the mode of drawing up the analysis. By the pro- 

 cess 5, twelve cubical inches of gas have been expelled during 

 the ebullition of a pint of water. The exposure to solution of 

 potassa has occasioned a diminution of eleven cubical inches, 

 which, it having been previously ascertained that no sulphu- 

 retted hydrogen was present, may be considered as carbonic 

 acid. The remaining gas thrown up into a tube, containing a 

 portion of phosphorus, and heated, suffers scarcely any dimi- 

 nution, and the phosphorus does not burn : hence it may be 

 regarded as nitrogen. The gaseous contents, therefore, of the 

 water under examination are, in the wine pint — 



Carbonic acid II cubic inches. 



Nitrogen , 1 ditto *. 



If sulphuretted hydrogen be present, it is best to have re- 

 course to a separate operation to estimate its quantity : for this 

 purpose collect the gas as before, and throw up into it a small 

 quantity of alcoholic solution of iodine. The absorption de- 

 notes the quantity of the gas. (8). 



14. The next step of the operation relates to the examina- 

 tion of the precipitate, which has been deposited during 

 ebullition, 9. A. Let us suppose the weight of oxalate of lime 

 to be 3 grains, of oxide of iron 1 .5 grain, and of magnesia I 

 grain, then the above data give 



Grains. 

 Carbonate of lime 2.2 



Carbonate of iron 2.4 



Carbonate of magnesia . , . , 2.1 



15. The alcoholic solution (10) may be diluted and tested by 

 oxalic acid for lime ; if absent, evaporate to dryness as di- 

 rected. Let us suppose the residue to be 



Muriate of magnesia 5 grains. 



* Of this nitrogen, a small portion will probably have been derived from 

 the air in the tube connecting the flask with, the pneumatic apparatus ; a 

 little practice soon enables the operator to ascertain when it has been ex- 

 pelled ; or it may be received entire, and afterwards deducted frora the 

 whole produce. 



