90 ANALYSIS OF SOILS. 



The fubftance remaining after the adlion of the acid, may 



be confidered as filicious; and it muft be feparated and its 



weight afcertained, after wafhing and drying in the ufual 



manner. 



Carbonate of Thealumine and the oxide of iron, if they exift, are both 



n^cdi! W * diflblved b y the ful P huric acid ; the )' mav be Separated by 

 mine, carbonate of ammoniac, added to excefs ; it throws down the 



alumine, and leaves the oxide of iron in folution, and this 

 fubftance may be feparated from the liquid by boiling. 



Should any magnefia and lime have efcaped folution in the 

 muriatic acid, they will be found in the fuiphuric acid ; this, 

 however, is fcarcely ever the cafe; but the procefs for 

 detecting them and afcertaining their quantities, is the fame 

 in both inftances. 

 More accurate The method of analyfis by fuiphuric acid, is fufficiently 

 procefs. precife for all ufual experiments; but if very great accuracy 



be an object, dry carbonate of potafh muft be employed as 

 the agent, and the refiduum of the incineration muft be heated 

 red for half an hour, with four times its weight of this fub- 

 ftance, in a crucible of filver, or of well baked porcelain. 

 The mafs obtained muft be diflblved in muriatic acid, and the 

 folution evaporated till it is nearly folid ; diftilled water muft 

 then be added, by which the oxide of iron and all the earths, 

 except filex, will be diffolved in combination as muriates. 

 The filex, after the ufual procefs of lixiviation, muft be heated 

 red ; the other fubftances may be feparated in the fame 

 manner as from the muriatic and fuiphuric folutions. 



This procefs is the one ufual ly employed by chemical phi* 

 Jofophers for the analyfis of ftones. 



XII. Mode of difcovering foluble Animal and Vegetable 

 ■ Matter, and Saline Matter, 



Matter* foluble If any faline matter, or foluble vegetable or animal matter, 

 in water. » g f u fp e ft ec j j n , t h e foil, it will be found in the water of lixivia- 



tion ufed for feparating the fand. 



This water muft be evaporated to drynefs in an appropriate 

 difli, at a heat below its boiling point. 



If the folid matter obtained is of a brown colour and inflam- 

 mable, it may be confidered as partly vegetable extracl. If 

 its fmell, when expefed to heat, be ftrong and fetid, it 

 contains animal mucilaginous or gelatinous fubftance; if it be' 



white 



