CHAP. ii. SUPERPHOSPHATE OF LIME. 1013 



process was afterwards applied to ground coprolites and various other 

 forms of mineral phosphates, the manure so made being known as 

 mineral superphosphate, to distinguish it from " dissolved bones." 

 The raw phosphatic material for the manufacture of superphosphate, 

 which is now an enormous chemical industry, is found in almost all 

 quarters of the world. Very large supplies of phosphate occur in 

 South Carolina, very similar in composition to our own Cambridge 

 Coprolites, while other descriptions of phosphatic mineral, such as 

 apatite, are found in Canada, Norway, France, Belgium, Germany, 

 Spain, and the West Indies. At present the chief sources, perhaps, are 

 Algeria and Florida. Phosphatic guanos, too, are found in many parts 

 of the world besides Peru, and these are generally used for making high- 

 class superphosphates or concentrated compound manures. Peruvian 

 guano itself is also "dissolved," and, by the addition of sulphate of 

 ammonia to make its action more rapid, is converted into a rich 

 ammoniacal superphosphate, known as " Dissolved Peruvian Guano." 



Experiments have demonstrated the fact that the conversion of mineral 

 phosphates into superphosphate is not absolutely necessary to fit them 

 for plant food. Very fine grinding will answer the purpose, but less 

 satisfactorily; and there is no doubt that the simplest and most 

 economical mode of using mineral phosphates is to make them into 

 superphosphates. In cases where circumstances render the use of a 

 non-acid or undissolved manure desirable, there are other sources of 

 phosphate bones, guano, fish-guano, or basic slag (presently to be 

 described), which are all better than ordinary mineral phosphates merely 

 ground. 



The farmer must discriminate between real "dissolved bone" and 

 the mixed manures now generally sold under the name of " dissolved 

 bone compound" which are made of mineral superphosphate mixed 

 with some bone, blood, &c., and which yield less ammonia than pure 

 dissolved bone. 



BASIC SLAG. This is, comparatively speaking, a new manure. It 

 consists of the slag obtained in removing, by a certain metallurgical 

 process, the phosphorus with which iron, made from most English 

 iron ores, is largely contaminated, and when ground to an impalpable 

 powder it forms a cheap and useful manure. When it was first put on 

 the market, it was regarded by unscientific men with some suspicion, 

 as a bye-product of steel works seemed to them an incongruous 

 substance for use as a fertiliser. In the course of a few years, however, 

 it came into extensive use on the large moorland tracts on the Continent 

 of Europe, and its employment has steadily increased in this country 

 until it has, on much of our land, come to be regarded as indispensable, 

 especially on heavy grass land on which it greatly encourages clover. 

 It is especially suitable for use on land poor in lime as well as phosphates. 

 Some soils contain so little lime that superphosphate is scarcely suitable 

 for them, and on these especially on heavy land basic slag gives 

 excellent results. On very light land bone meal is perhaps better. The 

 phosphoric acid in basic slag does not exist as tribasie phosphate, but 



