262 



THE SOUTHERN PLANTER. 



bone dust, bone black, wood ashes, etc., 

 would have reduced the proportion of so- 

 luble phosphate, without returning an 

 equivalent. 



Again, let us take the superphosphate 

 prepared from bone black ; I have already 

 shown that the theoretical amount of solu- 

 ble phosphate in this should be about 32 

 per cent., equivalent to 46^ per cent, of 

 neutral phosphate. Allowing that there re- 

 mains 25 per cent, of the neutral phos- 

 phate untouched by the acid, the manure 

 ought still to contain some 24 per cent, of 

 soluble phosphate, which would be reduc- 

 ed to 18 per cent, by the addition of 25 per 

 cent, of guano, then the manure would con- 

 tain about 18 per cent, of soluble phos- 

 phate of lime, 16 per cent, neutral phos- 

 phate, 4 per cent, ammonia, and a larger 

 proportion of plaster than in the last case. 



Superphosphate of lime is sold to far- 

 mers at from $40 to $50 per ton of 2,000 

 lbs., the prices varying with the brands.; — 

 Now it can be shown by a very simple 

 calculation, that the materials required for 

 its manufacture, to wit: sulphuric acid, 

 bone dust, bone black, guano, etc., are sold 

 at such prices that the manufacturer would 

 realize a handsome profit from his manure, 

 supposing it to come fully up to the stand- 

 ard of the two samples just referred to. 



I repeat, therefore, in view of these facts, 

 that superphosphates which have had no 

 manure containing ammonia mixed with 

 them, and which consequently contain but 

 from 1 to 1^ per cent, of ammonia, should 

 on analysis yield from 16 to 18 per cent, 

 of soluble phosphate, from 8 to 10 per 

 cent, of neutral phosphate of lime, together 

 with a due proportion of plaster, &c. — 

 And that those to which guano or some 

 salt of ammonia has been added, by which 

 a very material increase in the proportion 

 of ammonia has been made, should con- 

 tain from 12 to 16 per cent, of soluble 

 phosphates, some 15 per cent, of neutral 

 phosphate of lime, together with the plas- 

 ter due to the sulphuric acid consumed. 



Let us now look at the composition of a 

 few of the superphosphates in the market. 

 De Burg's is probably better known, and 

 more extensively used than any other. So 

 many certificates are published in relation 

 to the very great superiority of this ma- 

 nure, and so much is said about subject- 

 ing each supply to analysis by well known 

 chemists, etc., that I must confess I com- 



menced this investigation with the settle 

 conviction that De Burg's superphosphat e 

 would f urnish me with a practical standard 

 of excellence for manures of this class, to 

 which I could refer all pothers — the sequel 

 will show how far my expectations have 

 been realized. 



I have analyzed two samples of De 

 Burg's superphosphate; the analyses were 

 not what chemists term complete in all re- 

 spects, but sufficiently so for all practical 

 purposes. The first one examined had 

 been, in my possession for several years ; 

 it was made about the time, or soon after, 

 De Burg commenced the manufacture of 

 superphosphate, and had been sent out for 

 distribution among farmers, that they might 

 test its virtues, and was no doubt intended 

 as the ne plus ultra of superphosphates. — 

 This sample contained about 5 per cent, of 

 ammonia, 6| per cent, of soluble or real 

 superphosphate of lime, some 30 per cent, 

 of neutral phosphate of lime, together 

 with about 30 per cent, of plaster, and 

 small quantities of other less valuable 

 constituents. The manure had been pre- 

 pared from bone black by the action of 

 more or less sulphuric acid, with the after 

 addition of some Peruvian guano, and pro- 

 bably a little sulphate of ammonia. When 

 these results were first obtained, 1 thought 

 that the manure had been made in good 

 faith, that originally there had been a 

 much larger proportion of soluble phos- 

 phate, and that the phosphoric acid had 

 been precipitated by the after use of the 

 guano ; I am now satisfied, however, that 

 there never could have been more soluble 

 phosphate than the manure now T contains, 

 because I have ascertained that the addi- 

 tion of guano will not precipitate the neu- 

 tral phosphate of lime. 



The second sample I obtained direct 

 from the agent in Baltimore, and may be 

 regarded as a fair average of the manure 

 now offered by Mr. De Burg and his agents 

 to Southern farmers. With the manure 

 the agent sent me an analysis, from which 

 I naturally concluded that it was a very 

 superior article. 



This analysis gives us 7 per cent, of 

 ammonia, 41 per cent, of phosphates 

 (without saying, however, how much is so- 

 luble phosphate,) etc., and says there are 37 

 parts soluble in cold water, from which one 

 would naturally infer that there must be a 

 very considerable proportion of soluble 



