Composition and Value of Guano. 221 



and it will be necessary to allow 10 per cent, for moisture and 

 accidental impurity. 



The sulphate of ammonia of commerce will contain in 100 

 parts and in a ton respectively — 



In 100 parts. In a ton. 



Ammonia . . . 20*4 . . 457 lbs. 



Sulphmic Acid . . 48-0 . . 1,075 „ 



Water .... 31-6 . . 708 „ 



100- 2,240 „ 



Here it will be seen that to procure 1 ton of ordinary sulphate 

 of ammonia about \ ton (dry) sulphuric acid must be em- 

 ployed. Sulphuric acid which has not undergone the final and 

 expensive evaporation — that is to say, acid of specific gravity 1*70 

 (see note in Appendix) — can be bought for about 5/. a ton. Ac- 

 cording to the calculation in the Appendix below, the quantity of 

 such acid necessary to form a ton of sulphate of ammonia will be 

 worth 3/. 14*. ^d. 



£. s. d. 

 Deducting from the value of a ton of sulphate of ammonia . 12 

 The value of the acid used in its preparation . . , 3 14 4^ 



We have . 8 5 7^ 



as the value of the ammonia in a ton of the salt, leaving out, of 

 course, in this case all calculation of the cost of labour, &c. 



From the above facts it would appear that a high value was 

 placed upon the ammonia by the gas-manufacturer ; but, in truth, 

 it is not so. As a product of very secondary importance in rela- 

 tion to that of the gas itself, it is not usually worth his while to 

 embarrass his operations with its preservation ; whilst, on the 

 other hand, he views the difficulty of its removal as an imper- 

 fection of his process, and would liberally encourage any improve- 

 ment which could be suggested. We .can only then conclude, that 

 of the 12Z. a ton paid for sulphate of ammonia, 8/., or two-thirds 

 of the sum, represents the expense of manipulation. 



Again ; the sum of 3Z. 145., as the expense of the acid, suggests 

 the desirableness of discovering some comparatively inexpensive 

 substance for the absorption of the ammonia. There is good 

 reason to hope that the ingenuity and industry of those who apply 

 themselves to these manufacturing processes will sooner or later 

 be rewarded by the discovery of an economical means of sepa- 

 rating the ammonlacal compounds without injury to the illu- 

 minating power of the gas itself; and then, and not till then, will 

 this source of ammonia assume the importance which it merits. 



If we assume that in sulphate of ammonia the only ingredient 

 of value in an agricultural point of view is the ammonia, its price 

 will be 65^. per lb. It may be fairly objected to this mode of 



