FIELD EXPERIMENTS ON MANURE CONSTITUENTS, 169 



similar substances, are slow-acting fertilizers, which have to be transformed 

 into soluble combinations before they can benefit plants. 



3. That ammoniacal salts are more energetic fertilizing matters, which, 

 however, are fixed in the soil at first, and retained in it during the colder 

 periods of the j'ear, and which are gradually changed into nitrates and 

 rendered soluble during the most active period of plant-growth. 



4. That, in the shape of nitrates, nitrogen is not only the most active, but 

 also the most abundant and common combination from which plants derive 

 their nitrogen. 



2nd Part : On the solubility of pJiosphate of lime in various forms of phos- 

 phate of lime and phospliate of magnesia, in pure distilled water, and in 

 various saline solutions. 



Solubility of various phosphatic matters in distilled water. 



The amount of phosphate of lime which water is capable of taking up 

 from different materials depends. amongst other circumstances, on the physical 

 condition of the materials. 



Thus, hard crystalline phosphatic materials, even when finely powdered 

 and left a long time in contact with water, do not yield so much phosphate 

 of lime to water as more porous substances in a shorter period. 



In the following experiments, a considerable excess of the finely powdered 

 materials was mixed with about half a gallon of cold distilled water, and 

 repeatedly shaken up from time to time and left in contact with the water 

 for a week, except otherwise stated. The clear liquid was then drawn off 

 with a siphon, and filtered perfectly clear. A pint was then evaporated to 

 dryness, the residue dissolved in as little hydrochloric acid as possible, then 

 precipitated with ammonia, and in some instances the precipitated phos- 

 phates were redissolved and thrown down a second time with ammonia. 



In experimenting with phosphatic minerals, it is not sufficient merely to 

 evaporate the watery solution to dryness ; for, besides phosphate of lime, 

 water dissolves more or less carbonate of lime, magnesia, traces of alkalies, 

 &c., which, added to the weight of the phosphate of lime, in many instances 

 would give the latter far too high. In each case 2 pints of liquid were 

 evaporated separately, and the following results obtained : — 



Amount of phosphate of lime 

 (3CaO, POj) dissolved in 

 1 pint. per gallon. 



Exp. gTs. grs. 



Pure tribasic phosphate of lime, precipitated, burnt, 1 1st '28 2'24 



and finely ground f 2nd '27 2*16 



Pure tribasic phosphate of lime, precipitated and 1 1st "72 5'76 



still moist J 2nd '67 5-36 



Pure bone-ash, made from the shank-bone of ahorse, I 1st '13 1'04< 



washed with water for a long time before trying I 2nd '17 1*36 



the solubility in water. (This bone-ash was made j 3rd 'l* 1*12 



of a very solid bone.) J ■ith '15 1*20 



Amount of tribasic phosphate of 

 lime dissolved in 

 1 pint. per gallon. 



Exp. grs. grs. 



Commercial sample of American bone-ash ■{ i , JB^ 2^ 



^ \2nd -22 1'76 



It will be seen that precipitated phosphate of lime in a moist condition is 



