42 AGRICULTURAL CHEMISTRY. 



clay is a silicate of alumina, composed of about 60 per 

 cent, of silica, and 40 of alumina. 



61. Chloride of Sodium (NaCl) is composed of 

 one atom of chlorine, 36, to one of sodium, 23. (See 

 Table I.) It is no other than common salt. As corn, 

 potatoes, and turnips contain large amounts of both 

 its ingredients, it would seem hardly possible but that 

 it should prove beneficial to these crops, especially on 

 lands where either of them have been raised so long 

 as to have exhausted the soil of the chlorine and so- 

 dium origmally contained in it. 



62. Sulphuretoflron (Table IL, 16). — There are three 

 combinations of sulphuret and iron. 



1st. The protosulphuret of iron (FeS), consisting 

 of one atom of iron (Fe) to one of surphur (S). 



2nd. The sesquisulphuret (Fe^'S^), consisting of two 

 atoms of iron to three of sulphur. 



3rd. The bisulphuret (FeS^*), consisting of one 

 atom of iron to two of sulphur. This last is often 

 called fool's gold, from its strong resemblance to that 

 metal. 



63. Sulphuret of Hydrogen^ or sulphuretted Hydro- 

 gen (HS), is a combination of one atom of sulphur, 

 16, to one of hydrogen, 1, making the atom of the 

 compound 17. The nitrogenous, or azotized parts of 

 plants and animals, contain a little sulphur and a very 

 little phosphorus. When those, substances which con- 

 tain sulphur, as wool, hair, horns, hoofs, and eggs, de« 



