CHEMICAL DEPARTMENT. 35 



Superphosphates. — Phosphates dissolved with sulphuric acid. Their 

 composition varies according to the richness of the phosphate from which 

 they are made, and the extent to which they have been dissolved. 



High-class Super fliosphates are made from phosphates containing a high 

 percentage of phosphate of lime, and are very thoroughly dissolved. They 

 should contain between 30 and 40 per cent, soluble phosphate, and very 

 little insoluble phosphate. 



Medium Supeiyhosphates contain at least 26 per cent, soluble phosphate, 

 and all below that are 



Loiv-class Supeiyhosphates made from minerals poor in phosphate of lime, 

 or insufficiently dissolved. 



Mineral Phosphates exist in great variety, and contain very various pro- 

 portions of phosphate of lime, viz., from 20 to 90 per cent. They are of use 

 as manures only when they are ground to the finest flour. 



Basic Cinder. — A substance obtained as a waste ^^I'oduct in the dephos- 

 phorising of steel. It contains about 40 per cent, phosphate of lime, and 

 is manufactured into a jjowder of extreme fineness. It is a good manure, 

 and cheap. Especially appropriate for moory land. 



Compound Manures. — These are general manures containing nitrogenous 

 matter, phosphates, and potash, and their value depends not only on the 

 amounts of these constituents, but also on their fineness of division, their 

 solubility, and the sources from which their ingredients are derived. 



The general character of a few of the more common of these may be 

 indicated thus : — 



Turnip Compounds. — These usually contain from 25 to 35 per cent, 

 phosphates, of which the half or more is soluble, and nitrogenous matter, 

 capable of yielding from 2 to 4 per cent, of ammonia, and sometimes 1 or 2 

 per cent, of potash. 



Potato Compounds. — These are somewhat like the preceding, but contain 

 usually less phosphate and a little more ammonia, from 3 to 6 per cent. ; 

 sometimes they contain no potash, but more frequently about 3 or 4 per 

 cent, is present, and in some instances twice as much. 



Bean Compounds. — These may contain from 10 to 20 per cent, phosphates, 

 nitrogenous matter yielding from 2 to 4 per cent, of ammonia, and usually 

 a considerable proportion of potash, often as much as from 10 to 20 per cent. 



Cereal Compomids. — These usually contain about 20 per cent, phosphates, 

 mostly soluble, and nitrogenous matter, partly as nitrates, yielding from 

 3 to 6 per cent, ammonia, and they may also contain potash. 



Grass Compounds. — These are somewhat like the preceding, but may 

 contain less phosphates and more nitrogen, part of which is usually in 

 the form of nitrate. 



KELATIYE ACTR^ITY OF MANURES. 



Nitrogen. — Most active in — 1st, Nitrates ; 2nd, Ammonia salts ; 3rd, 

 High-class Peruvian and Ichaboe guanos ; 4th, High-class dissolved com- 

 pounds ; 5th, Dried blood ; 6th, Steamed bone flour ; 7th, Fish guano and 

 fine bone meal ; 8th, Eape cake and cotton cake dust ; 9th, Bone dust and 

 crushed bones. 



Phosphates. — Most active in — 1st, Superphosphates and dissolved phos- 

 phates derived from any source ; 2nd, Precipitated and re^i'erted j>hos- 

 phates ; 3rd, Steamed bone flour ; 4th, Bone ash ; 5th, Charleston and 

 similar phos^Dliates ground to the finest flour ; 6th, Bone meal and fish 

 guano ; 7th, Bone dust and crushed bones. 



