SCIENCE OF AGRICULTURE. 113 



Sulphuric and Phosphoric Acids. — Sulphuric acid is 

 a combination of three parts of oxygen gas, two parts 

 of sulphur by weight. Phosphoric acid is composed 

 of about one and a half parts of phosphorus and one 

 of oxygen, by weight. Sulphur is a well known 

 substance. Phosphorus is contained in urine and 

 other animal matter, is easily set on fire by friction, 

 and is now in common use on friction matches. 



Oxygen gas is one of the most important agents in- 

 the operations of nature. Mixed with azote, twenty 

 one parts of oxygen, and seventy nine of azote, it 

 forms atmospheric air. 



Azote, or Nitrogen, — This gas, which is only mix- 

 ed, not combined with oxygen in the atmosphere, 

 combines also with oxygen in different proportions, 

 forming nitrous acid, or aquafortis, nitric acid, &c. 

 Substances, which, although composed of the same 

 constituents as atmospheric air, are extremely acrid, 

 corrosive, and destructive to both vegetable and ani- 

 mal matter, living or dead. Combined with chlorine, 

 another gas, which I shall not now describe, it forms 

 the most extraordinary and powerful explosive sub- 

 stance known.. A single grain of it, (Troy weight,) 

 is as much as any chemist dares to experiment upon. 

 It explodes with prodigious violence when heated to 

 212°, the heat of boiling water, or, when touched 

 by any oily or greasy substance. At present, we 

 know of no use to which it is applied in the arts. 

 But there can be but little doubt, it will at some fu- 

 ture time become a more powerful agent of man than 

 he has ever yet subdued to his despotic control. 

 By its aid perhaps, mountains of rock may be crum- 

 bled to dust for agricultural or other purposes. 

 Azote is a constituent part of animal matter. Its 

 agency in the process of vegetation is not well known. 



Oxygen one part, and hydrogen two parts, by 

 measure, burned together produce water. Hydro- 

 gen is called inflammable air, is the lightest of all 

 gases ; with it balloons are inflated ; and combined 

 with carbon is extensively used for lighting cities. 

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