ON THE ESTIMATION OF POTASH AND PHOSPHORIC ACID. 35 



the estimation of the " reduced " phosphates would often be rendered super- 

 fluous. 



The actual mode of occurrence of some of the constituents of manures is 

 very uncertain, and although interesting in a strictly scientific sense, is of 

 very limited practical importance. The Committee is of opinion that the 

 methods of statement now generally adopted are sufficient for commercial 

 purposes ; but with the view of securing greater uniformity in the statement 

 of rosults by different chemists the adoption of the following plan is 

 recommended : — 



Statement op the Results of Analysis op Commercial Phosphates. 



With respect to the mode of statement of the results of analyses of manu- 

 factured phosphates the Committee holds the following opinions : — 



"When found in quantities greater than traces, the proportions of oxide of 

 iron and alumina in the sample should always bo stated, and also their 

 equivalents of the corresponding phosphates (JFe P0 4 and Al P0 4 ) and the 

 equivalent of the latter in tricalcic phosphate. Hence that item would 

 appear somewhat as follows : — 



Oxide of iron and alumina A°/ 



(Equal to phosphates of iron and aluminium . . B°/ ) 

 (Equal to neutral phosphate of calcium C°/ ) 



If it be proposed for any reason to state the iron and aluminium as phos- 

 phates instead of oxides the following form would be suitable : — 



Phosphates of iron and aluminium B°/ 



(Equal to neutral phosphate of calcium C°/ u ) 



(Containing anhydrous phosphoric acid D°/ ) 



The object of stating the equivalents in phosphate of calcium and phos- 

 phoric acid is to give the manufacturer or purchaser an estimate of the 

 tendency of the sample to " go back " owing to tho formation of reduced 

 phosphates. 



The Committee is of opinion that the soluble phosphate in a manure pre- 

 pared with acid is best stated as acid calcium phosphate, though in some 

 cases it may be questioned whether it wholly exists in that form. The term 

 " bi-pbosphate " should as far as possible be abandoned ; but as this cannot 

 bo done suddenly it is recommended that the equivalent of CaH 4 (P0j„ in 

 Ca P., O e should also be given. It is likewise desirable to state the equivalent 

 amount of bone phosphate (Ca 3 (P0 4 ) 2 ) from which the soluble phosphate 

 has been derived. Hence the statement of the soluble phosphate will be 

 somewhat as follows : — 



Soluble acid phosphate of calcium E% 



(Equal to so-called bi-phosphate of lime E%) 



(Equal to neutral phosphate of calcium (bone 



phosphate) made soluble Gc°/ ) 



(Containing anhydrous phosphoric acid H%) 



The statement of the insoluble phosphate presents no difficulty. 



The Committee is not prepared to make any recommendation respecting 

 the statement of the calcium sulphate, but is of opinion that whether the 

 anhydrous or the hydrated substance is entered as existent in the sample, 

 tho equivalent of the other should also be added in parenthesis. 



The Committee believes that it has clone all in its power to secure tho 

 objects for which it was appointed, and therefore presents this as its first 

 report. 



1)2 



