106 



THE GENESEE FARMER. 



seven of these samples with the following result : 

 5.23, 4.18, 3.89, 4.18, 4.89, 5.08, and 5.03 per cent. 

 Three of the samples slightly exceed our estimate, 

 and four fall below it. The average is 4.57, or 

 nearly one-half of one per cent, less than our 

 estimate. 



The other statement which Dr. Lee criticises is 

 the following. "We give the Professor's own words : 



"But the most interesting and, it strikes us, 

 extraordinary statement of the editor of the Farmer 

 is the following : ' The value of this change (the 

 conversion of insoluble bone into a soluble mass) 

 may be understood by the consideration of tlie fact 

 that, -while insoluble phosphate sells in London at 

 less than one cent per lb., the soluble phosphate 

 sells readily, as a manure for turnips, at eight cents 

 per lb.' 



" If the word eight was not printed, and the 

 number expressed by the figure 8, we should have 

 regarded it as a typographical error ; for eight cents 

 & lb. for a superphosphate of lime to apply to a 

 turnip crop, is paying $80 for a thousand lbs., and 

 of course $160 for a ton of two thousand lbs." 



That is so. Doctor ! Eight cents a lb. is $80 for 

 1,000 lbs., and $160 for a ton of 2,000 lbs. No 

 doubt about that ! But we did not say that what 

 ij called " superphosphate of lime " sells in London 

 fur eight cents per lb. We said " soluble phosphate " 

 sells for eight cents per lb. ; and it certainly can not 

 be bought in any market for less than that. 



Prof. S. W. Johnson, in his valuable Report on 

 Commercial Manures, etc., to the Connecticut State 

 Agricultural Society, says: "Prof. Way, chemist 

 to the Royal Agricultural Society of England, esti- 

 mates the worth of soluble phosphoric acid at 10-^ 

 cents, per lb. Dr. Voelcker, of the Royal Agri- 

 cultural College of England, and Dr. Stockhakut, 

 the distinguished Saxon agricultural chemist, reckon 

 it at 12^ cents. They have deduced these prices 

 from that of the best commercial superphosphates. 

 In this report, the price will also be assumed at 12^ 

 cents. This, I believe, is considerably more than 

 it is really worth, but it is probably the lowest rate 

 at which it can now be purchased." 



Why this statement of an admitted fact should 

 ■puzzle the Pi'ofessor, we were for some time at a 

 lioss to comprehend. But by reading another article 

 on " Commercial Manures " from Dr. Lee, in the 

 ■previous number of his paper, we have discovered 

 the cause of his surprise. 



Dr. Lee evidently tliinks that what is called 

 superphosphaifce of lime, and sold under this name 

 in market, is^ or ought to bo, composed of soluble 

 phu'sphate — or, in other words of superphosphate. 

 A little examination will show our friend that he 

 is mistaken. The common bone-phosphate of lime 

 is composed of three atoms of lime and one of 



phosphoric acid. Superphosphate of lime is con 

 posed of one atom of lime, two of water and oi; 

 of phosphoric acid. To convert the common insf 

 luble phosphate into the soluble superphosphat* 

 we have to take away two atoms of lime. This 

 done by adding sulphuric acid to the ])one-pho. 

 phate. The sulphuric acid has a stronger .illinit 

 for the lime than phosphoric acid, aiul if siiliiiMt.M 

 sulphuric acid was added, it would take away a 

 the lime, and leave the phosphoric acid free, lii 

 the object is to take away two- thirds only of t!^ 

 lime, and we add only sufficient fur this purpose. 

 The sulphuric acid unites with the two atoms ( 

 lime, and forms sulphate of lime. This sulphate < 

 lime, or plaster, remains in the mixture. It c: 

 not be separated. Dr. Lee appears to overlook tl 

 fact, and hence his surprise at our statement tl: 

 soluble phosphate sells in London for eight cen 

 per lb. Superphosphate of lime is not compos, 

 wholly of soluble phosphate. It necsss&rily contai 

 plaster and a considerable quantity of water. 



Dr. Lee speaks of a "true bi-phosphate of lin 

 when free from iDatery Now, our critical friei 

 should know that there is no such article, and c: 

 not be. In converting bone-phosphate of lime 



Lime (25), lime (28), lime (28), phosphoric acid (T2;. 

 into superphosphate of lime. 



Lime (28), waler (9), water (9), phosphoric aciJ (72). 



the two atoms of lime taken away by the suli)hiii 

 acid are replaced by two atoms of water. TI 

 water is essential to tlie change. It acts as a ba 

 instead of lime. And it would be just as reas( 

 able to speak 'of a true bi-phosphate of lime wli 

 free from lime, as of a "true bi-phosphate of lii 

 when free from water."* 



Speaking of Rhodes superphosphate of lime, t 

 Professor says: "Does not the fact that our bi 

 American superphosphate of lime has only fourtc 

 per cent, of this substance (soluble phosphate) 

 it, go far to prove that our agi-icultural libraries a 

 reading are strikingly defective. * * So long u 

 the public mind loves ignorance of the agricultu 

 experience of all mankind, save a man's dear st 

 better than it loves anything else, why sliould a 

 manufacturer of superphosphates be at the exper 

 of supplying the public with an article that contai 

 twenty-eight or fifty-six per cent, of the thi 

 advertised, when fourteen will satisfy the intel 

 gence of the community?" 



* In the manufacture of superphosphate of lime, the calcir 

 bones should always bo mixed with about 75 per cent, of wat 

 before the acid is added. We know it is generally recommend 

 to add the water to the acid, but it is much better to thorougli 

 wet the bones instead. We state this as the result of conside 

 ble experience. 



