114 HOW CROPS GROW. 



ing organism existed in union with organic acids ; the lat- 

 ter being destroyed by burning. 



It also occurs in combination with lime in the tissues of 

 many plants. Its compounds with bases arc carbonates, 

 to be noticed presently. When a carbonate, as marble or 

 limestone, is drenched with a strong acid, like vinegar or 

 muriatic acid, the carbonic acid is set free with effer- 

 vescence. 



Cyanogen, Sym. CN. This important compound of Carbon and 

 Nitrogen is a gas which has an odor resembling that of peach-pits, 

 and which burns on contact with a lighted taper with a fine purple flame. 

 In its union with oxygen by combustion, carbonic acid is formed, and 

 nitrogen set free, 



Cyanogen may be prepared by heating an intimate mixture of two parts 

 by weight of ferrocyanide of potassium, (yellow prussiate of potash,) and 

 three parts of corrosive sublimate. The operation may be conducted in 

 a test tube or small flask, to the mouth of which is fitted a cork pene- 

 trated by a narrow glass tube. On applying heat, the gas issues, and 

 may be set on fire to observe its beautiful flame. 



Cyanogen, combined with iron, forms the Prussian blue of commerce, 

 and its name, signifying the blue-producer, was given to it from that cir- 

 cumstance. 



Cyanogen unites with the metallic elements, giving rise to a series of 

 bodies which are termed Cyanides. Some of these often occur in small 

 quantity in the ashes of plants, being produced in the act of burning by 

 the union of nitrogen with carbon and a metal. For this result, the 

 temperature must be very high, carbon must be in excess, the metal 

 is usually potassium or calcium, the nitrogen maybe either free nitrogen 

 of the atmosphere or that originally existing in the organic matter. 



With hydrogen, cyanogen forms the deadly poison hydrocyanic or prus- 

 sic acid, H Cy, which is produced from amygdaline, one of the ingre- 

 dients of bitter almonds, peach, and cherry seeds, when these are crush- 

 ed in contact with water. 



When a cyanide is brought in contact with steam at high temperatures, 

 it is decomposed, all its nitrogen being converted into ammonia. 



Cyanogen is a normal ingredient of one common plant. The oil of 

 mustard is the sulpho-cyanide of allyle, C 3 II 5 CNS. 



SULPHUR AND ITS COMPOUNDS. 



Sulphur', Sym. S, at. wt. 32. The properties of this 

 element have been already described, (p. 42.) Some of 



