THE 'AORICULTURAL JOURNAL. 



717 



c )mmon language is called enperphos- 

 pliate or acid phosphat '. 



If two ptrtions if IjyJiogeii are re- 

 placed we get : — 



calcium phosphorus 

 calcium oxygen 

 hydrogen 



and this is known as di-calcic phosphate, 

 i.e., two-lime phosphate, and as reduced 

 or reverted phosphate. 



If the whole of the hydrogen is re- 

 placed there will be : — 



calcium phosphorus 

 calcium ( xygen 



calcium 



which is the ti-i-calcic or three-lime phos- 

 phate, bone phosphate or insoluble phos- 

 phate. For the purposes of these articles 

 the correct chemical names will generally 

 be used for the future, since the names 

 themselves, if once understood, describe 

 accurately which of the three forms is 

 meant, and prevent confusion. 



Tri-Calcic Phosphate. 



Of these three phosphates the tri c ilcic 

 must be considered the norniLd or natural 

 form, since it is the one always formed 

 when phosphoric acid and lime combine, 

 providing, of course, that a si.fficiency of 

 the latter is present. It is found in bone, 

 guanos, coprolites, and in various parts of 

 the world in the shape of phosphatic rocks 

 such as apatite, which are all classed as 

 mineral phosphates, some of them con- 

 taining as much as 80 or 90 per cent, of 

 phosphate. Tri-calcic phosphate is prac- 

 tically insoluble in pure water, but 

 readily dissolved by acids. If we bnrn a 

 bone in an open fire, we shall find it con- 

 verted into a Avhite, brittle, and easily 

 powdered mass, the animal matter having 

 been burnt away, and though not pure 

 phosphate, may be used to study its 

 characteristics. If a small portion be 

 powdered, and put into a glass with a little 

 water, it will refuse to dissolve, but when 

 a little hydrochloric acid is added, it will 

 gradually dissolve to a nearly clear solu- 

 tion. Kain water, containing as it does 

 some carbonic acid, slowly attacks and 

 dissolves it, and the weak acids of plant 

 roots have a similar power, the ease with 

 which this solution takes place depending 

 chiefly on the fineness of the powder. 

 We all know that bone is an excellent 



manure, and it mnst, therefore, get dis- 

 solved somehow ; but we also know it is 

 necessary to grind it to a fine dnst, and 

 thnt the fini r it is the quicker it acts. 

 Most guanos are naturally composed of 

 extremely fineparticlcs, and the substance 

 is in a soft C(mdition, and so easily at- 

 tacked by the roots of j^lan's ; but with 

 mineral phosphates the case is different ; 

 many of them are nearly as hard as glass, 

 and "allhough when finely — it must be 

 very finely— ground, they act slowly as a 

 feri'iliser, they are little used in this form, 

 owing to this very slowness. Even in the 

 case of bones it is often noticed that they 

 exert a fuller effect in the second and 

 third year than in the year of application. 

 Bones. 



As bones are so popular a manure they 

 are worth a little special notice. All 

 plants contain more or less phosphate, 

 especially in the seed, and thus animals 

 obtain in their food the amount required 

 to form their bony frame. Clean dry 

 bone contains about per cent, of tri- 

 calcic phosphate, 37 per cent, of animal 

 mutter similar to gelatine, and a 

 little chalk, magnesium phosphate, etc. 

 Ordinary fresh bone contains a consider- 

 able proportion of moisture, and in a 

 sample of bone-dust we may expect to 

 find 7 or 8 per cent. This moisture and 

 other unavoidable impurities reduce the 

 percentage of phosphate somewhat, so 

 that a good average sample of bone-dust 

 should give about 20 per cent, of phos- 

 phoric oxide and 25 per cent, of lime. 

 The animal matter contains nitrogen, and 

 this gives a further manurial value ; the 

 amount is usually from 3^ to '4 per cent. 

 Sometimes bone is steamed before grind- 

 ing ; this removes a good deal of the 

 animal matter, with its contained nitro- 

 gen, but renders the bone more easy to 

 grind ; accordingly, steamed bone is a 

 richer phosphatic fertiliser, but poorer 

 in nitrogen, than raw bone. Bones are 

 generally thought to give their best re- 

 sults on light soils, buteven on clays they 

 have proved a most useful manure. 

 Various plans have been proposed for 

 hastening their action by rotting or fer- 

 menting them ; one ol tlie best is to mix 

 raw bone with about a third of its weight 

 of clay, moisten the mass with the urine 

 of animals, and cover with a layer of 

 moist clay two or three inches thick. The 



