222 



On Superpfiospkate of Lime. 



substances so emplojed are animal charcoal, kelp, rape-cake, 

 shoddy, &c. Animal charcoal is itself a source of phosphate of 

 lime, and may consequently be added at any stage of the process. 

 Kelp is a substance prepared from the ashes of sea-weeds, and 

 contains a large proportion of alkaline carbonates ; its value as 

 an ingredient of superphosphate of lime appears to me question- 

 able — inasmuch as, although a certain quantity of alkaline phos- 

 phate may result from its admixture with the soluble phosphate, 

 much phosphate of lime is at the same time precipitated, and the 

 effect of using kelp will be to reduce the total quantity of phos- 

 phoric acid in solution. Rape-cake and shoddy may be useful 

 additions to a manure made from mineral phosphate only, but 

 are not necessary in the case of superphosphate made from bones 

 and acid only. 



The sulphate and muriate of ammonia are also added occa- 

 sionally to superphosphate of lime with advantage ; the latter, 

 however, by producing muriate of lime, causes the product to 

 attract moisture, and renders it very difficult of transportation. 

 Dried blood, which is becoming an article of considerable com- 

 merce, and which contains from 10 to 12 per cent, of nitrogen, 

 forms also a good addition to a mineral superphosphate, both as a 

 drying material and as supplying animal matter. 



Composition of Commercial Superphosphate of Lime. — Such being 

 the means at the disposal of the manufacturer, let us now see 

 what is the nature of the manure as actually supplied to the 

 farmer. During the last 2 or 3 years I have examined a very 

 large number of samples sent to me, in some cases by the buyers, 

 in others by the makers, of the manure. I shall select from these 

 such a number of cases as will illustrate the question and will 

 represent what, in my opinion, is the composition of a very 

 bad, and what of a very good, sample of superphosphate ; 

 and, as a practical mean, the analysis of samples of fair average 

 quality will be given, in proof that we are not v/ithout manure- 

 dealers possessing both principle and intelligence enough to 

 enable them to supply the agricultural public with a good 

 article. 



The annexed are analyses of some of the best samples of 

 superphosphate of lime which have come under my notice. 



The first of these samples contains the highest percentage of 

 soluble phosphate that I have as yet met with — it is almost 

 entirely a mineral superphosphate. Nos. 2 and 3 are excellent 

 specimens of the manure, containing, in addition to a large pro- 

 portion of soluble phosphate, a considerable amount of nitrogen ; 

 No. 4 is not so peculiar for its quantity of soluble phosphate as 

 for the combination with it of a very high percentage of nitrogen. 



