1916 J AGRICULTUEAL CHEMISTBY AGROTECHNY. 613 



fumes are disposed of by passing into a sink pipe which is washed with a stream 

 of water or in some other convenient manner. 



A small apparatus for two flasks is also described. 



Contribution to the determination of citric-acid-soluble phosphoric acid 

 by the iron-citrate method, N. Zachabiades and J. Czak {Ztschr. Landw. 

 Versuchsw. Osterr., 18 (1915), No. 7, pp. ^72-^75 ) .—Experimental data of the 

 analysis of a number of slags by the iron-citrate method are submitted. From 

 these data the authors conclude that the addition of hydrogen peroxid for the 

 purpose of oxidizing any hydrogen-sulphid combinations is usually superfluous, 

 especially if the odor of hydrogen sulphid is only weakly perceptible. The pre- 

 cipitate need not be filtered immediately, as has been previously recommended. 

 The data submitted check very well with results obtained by the procedxire of 

 Popp. 



Note on the determination of phosphorus in plant materials, A. W. 

 Chbistie (Jour. Indus, and Engin. Chem., 8 {1916), No. 6, p. 511). — Experi- 

 mental data submitted from the California Experiment Station indicate that the 

 ignition of the sample with magnesium oxid is a quick and accurate method of 

 oxidizing the organic material in the determination of total phosphorus. Oxida- 

 tion with fuming nitric acid was found to be unsatisfactory. 



Studies on the determination of sulphur as barium sulphate, P. L. Bltt- 

 MENTHAi, and S. C. Gueknsey (Iowa Sta. Research Bui. 26 (1915), pp. 390- 

 436). — The purpose of the investigation reported was chiefly "to discover the 

 magnitude and causes of the error involved in the usual method of determining 

 total sulphur, particularly in lime-sulphur solutions; ... to ascertain the 

 method best adapted to estimating total sulphur . . . and to extend our knowl- 

 edge of the mechanism of the reaction." The history and use of the method 

 are reviewed and discussed in some detail. 



Experimental results with potassium and sodium sulphates, showing the 

 effect of various rates of addition of barium chlorid in definite quantity and of 

 varying strengths at constant volume and acidity, demonstrate that there is 

 little choice between the use of 5 and 10 per cent barium chlorid, the time 

 of addition being slightly more important. Five per cent barium chlorid added 

 at the rate of 5 cc. per minute was found to yield the best average results in 

 the work at hand. Various strengths of acid were found not to influence the 

 results to any great extent, although a low acidity was preferable (2 per cent 

 or less). 



In studying the effect of various salts on the precipitation it was found 

 that when sodium salts were the only impurity very concordant analyses could 

 be obtained. In the presence of calcium the results obtained did " not differ 

 markedly from the figures obtained in the presence of other salts. The same 

 variations occur, and again the necessity of working under exactly uniform 

 conditions is emphasized." The presence of magnesium in general yielded high 

 values. From a general consideration of the analytical results the authors ar- 

 rive at the conclusion that " a pure precipitate of barium sulphate is not to be 

 obtained by any ordinary precipitation method. The best values are due to a 

 balancing of errors, and to insure uniformity of analyses the strictest attention 

 must be given to maintaining definite and identical conditions in the system." 



For accurate lime-sulphur analyses the following procedure is recommended : 

 One aliquot is oxidized with sodium peroxid, heated, diluted, acidified, boiled, 

 precipitated rapidly with 5 per cent barium chlorid, and filtered through a 

 Gooch crucible after an hour's standing. A general idea of the amount of sul- 

 phur in the definite volume of solution is thus obtained. The volume of the 

 final det«"mination is so adjusted that each cubic centimeter will contain 



