CHEMISTRY. 



939 



There were ranges of 1.25 and 4 per cent in the (leterniinations of moisture in 

 dupheate samples. The variations in the determinations of other constituents are 

 shown in the following tal)le: 



Voriations in triplicate determinations of various constiliicnls in tiro satnplcs of manure. 



Sample I. 



Constituents. 



Ash 



Nitrogen 



Potasli 



Phosphoric acid 



Per cent. 



11.39 



2.40 



3.22 



1.33 



(b) 



Per cent. 



11.19 



2.29 



3. 28 



1.29 



(c) 



Per cent. 



11.43 



2. 23 



3.25 



1.29 



Sample II. 



(a) 



Per cent. 



14.47 



2.22 



3. .55 



1.36 



(b) 



Per cent. 



16.11 



2.19 



3.46 



1.41 



(c) 



Per cent. 



16.27 



2.33 



3.60 



1.95 



' ' We may conclude from the foregoing facts that a large mass of manure can be 

 satisfactorily represented only by original samples of relatively large amount; that 

 the latter must be thoroughly subdivided under conditions unfavorable to heating, 

 and, so far as can be, to evaporation; that check weighings be made at every parting, 

 and that, when the material is sufficiently mixed, triplicate sul)samples should be 

 taken for separate determination of loss in air-drying, at least, in order to guard 

 against errors introduced by large ineciualities in the moistness of samples. Further- 

 more, it is clear that in handling large masses of manure greater accuracy of final 

 result will be secured by rapid weighing in large quantities on scales of low sensi- 

 tiveness than by weighing in small quantities on more sensitive scales, because of 

 the rapid drying which the manure undergoes under the latter conditions." 



The estimation of available phosphoric acid in manures, W. F. Sutherst 

 (Aiiah/yt, JS {1903), No. 324, p}>. G(!-7J). — Comparative determinations of the solubil- 

 ity of the phosphoric acid of basic slag, basic superphosphate, precipitated jihosphate, 

 and coprolite in 1 per cent citric acid and in solutions of potassium binoxalate, bitar- 

 trate and bimalate of the same degree of acidity as the citric-acid solution are reported. 

 The potassium-binoxalate and Ijitartrate solutions gave results on basic slag agreeing 

 quite closely with those obtained with 1 per cent citric acid. The potassium-bima- 

 late solution gave much lower results than the other solvents used. With the other 

 phosphatic materials tested the solvents gave very discordant results. From the 

 results of repeated extractions of basic slag and coprolite with 1 per cent citric-acid 

 solution the conclusion is drawn "that practii-ally the whole of the phosphoric acid 

 in any manure is available for plant food, but that in some it is assimilable in a 

 shorter time than others. Whether the usual method of testing the available plant 

 food and the results obtained by it give any definite idea of the amount a plant is 

 capable of absorbing or not, it seems from the experiments carried out that there is 

 certainly a relation between the amount dissolved and the amount whicli is in an 

 easily assimilable form, since the large proportion of phosphoric acid dissolved out 

 of the basic slag by one treatment with citric acid as distinguished from tliat removed 

 from coprolite in proportion to the total present easily accounts for the more rapid 

 effect of basic slag on a crop than that of a ground mineral phosphate." The ques- 

 tion as to what extent the action of the weak acid solvents used in determining the 

 availability of phosphoric acid imitates natural processes due to acid excretions from 

 tlie roots of plants is discussed at some length l)y the author and others, and the 

 ar))itrary character of such methods of determining availability of phosphoric acid 

 was ])ointed out. 



On the solution of insoluble calcium phosphate by means of ammonium 

 citrate solutions, K. Zulkowski and F. Cedivoda (Chem.Ind., ■^i! {1903), pp. 1-9, 

 37-33; ah.'<. in Chem. Centbl, 1903, I, No. S,pp. 477, ^75).— Investigati(jns are reported 

 which lead to the conclusion that solution of calcium phosphate in ammonium cit- 



26240— No. 10—03 2 



