THE VOLATILE PAET OF PLANTS. 45 



of the solution of pliosphoric acid obtained in Exp. 18. To one, add 

 some lime-water (see note p. 36) until a white cloud or precipitate is per- 

 ceived. This is a pjwsphate of lime. Into the other portion, drop solu- 

 tion of alum. A translucent cloud of phosphate of alumina is immediately 

 produced. 



In soils and rocks, phosphorus exists in the state of 

 such phosphates of lime, alumina, and iron. 



In the organic world the chemist has as yet detected 

 phosphorus in other states of combination in but a few 

 instances. In the brain and nerves, and in the yolk of 

 eggs, an oil containing phosphorus has been known for 

 some years, and recently similar phosphorized oils have 

 been found in the pea, in maize, and other grains. 



We have thus briefly noticed the more important char- 

 acters of those six bodies which constitute that part of 

 plants, and of animals also, which is volatile or destruct- 

 ible at high temperatures, viz. : carbon, hydrogen, oxygen, 

 nitrogen, sulphur, and phosphorus. 



Out of these substances chiefly, which are often termed 

 the organic elements of vegetation, are compounded all 

 the numberless products of life to be met with, either in 

 the vegetable or animal world. 



rLTIMATE OOMPOSITIOIT OF VEGETABLE MATTEE. 



To convey an idea of the relative proportions in which 

 these six elements exist in plants, a statement of the 

 ultimate or elementary percentage composition of several 

 kinds of vegetable matter is here subjoined. 



Grain of Straw of Tubers of Brain of May of Bed 

 Wheat. Wheat. Potato. Teas. Clover. 



Carbon 46.1 ■ 48.4 44.0 46.5 47.4 



Hydrogen 5.8 5.3 5.8 6.3 5.0 



Oxygen 43.4 38.9 44.7 40.0 37.8 



Nitrogen 3.3 0.4 1.5 4.3 3.1 



Ash, including sulphur )„, ^q ^q 31 77 

 and phosphorus J ' 



100.0 100.0 100.0 100.0 100.0 



Sulphur 0.13 0.14 0.08 0.31 0.18 



Phosphorus 0.30 0.80 0.34 0.34 0.30 



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