506 EXPERIMENT STATION EECORD. [Vol.37 



hours. The silicic acid becomes completely in.soluble, and after the addition 

 of water is separated by a filtration, washed free from chlorids, dried, and 

 weighed in the usual manner. 



A note on the phenolsulphonic acid method for nitrates in waters high in 

 magnesium salts, IM. S. Nichols {Jour. In4us. and Engin. Chem., 9 (1917), No. 

 6, pp. 586, 587). — To obviate the precipitation of magnesium and iron hydroxids 

 after neutralization of the excess phenolsulphonic acid, the addition of saturated 

 ammonium chlorid solution was found to be satisfactory. This modification 

 is deemed preferable to filtering the solution, as by the latter procedure a 

 small quantity of the color always remains in the filter. 



Note on the determination of strontium and lithium in water, S. D. 

 A\-ERiTT (Jour. Indus, and Engin. Chem., 9 (1917), No. 6, pp. 584, 585). — The 

 author, at the Kentucky Experiment Station, submits the following indirect 

 methods. 



For the determination of strontium, the weighed calcium and strontium oxids 

 are dissolved in hydrochloric acid, reprecipitated as oxalates, and then titrated 

 with standard potassium permanganate. For calculating the amount of stron- 

 tium oxid, the following formula is submitted : 



(W — CaO equivalent of KMnO, titration) 2.179=strontium oxid. 



W=weight of CaO and SrO. The derivation of the formula is explained. 



For the determination of lithium, the aqueous solution of the combined 

 chlorids of sodium, pot.'issium, and lithium is made up to a suitable volume, 

 from which an aliquot is taken for the determination of potassium. From 

 this determination the potassium and the potassium chlorid in the solution 

 are calculated. The total chlorin is determined in another aliquot by titration 

 with standard silver nitrate. The lithium chlorid Is then calculated by the 

 following formula : 



NaCl equivalent of C— CI in KCl— (W— KCl) X2.G4=!ithium chlorid. 



C=weight of total chlorin and W = weight of NaCl-fKCl + LiCI. 



Experimental data submitted indicate the accuracy of the procoiUiros. 



Improved chemical methods for differentiating bacteria of the coli- 

 aerogenes family, W. M. Clabk and H. A. Lvhs (Jour. liiol. Chem., SO (1917), 

 No. 2. pp. 209-23^. fig. 1). — A new medium for differentiating bacteria of the 

 coli-aerogenes family by accurate determination of the carbon dioxid and 

 hydrogen ratios and its use are described. The differences In the intensities 

 of the acid fermentations are determined by the use of the indicator method 

 of hydrogen ion concentration. 



The colorimetric determination of hydrogen ion concentration and its ap- 

 plications in bacteriology. W. M. Ci.ark and H. A. Lubs (Jour. Baet., 2 (1917), 

 iVo.f. 1. pp. 1-3^: 2. pp. 109-1S6; S, pp. 191-236, pi. 1, figs. 8).— A monographic 

 review, including the original work on the subject by the authors. 



It is concluded in general that with the improvements presented the colori- 

 metric method for the determination of hydrogen ion concentration is appli- 

 cable to routine as well as research purposes in bacteriology. 



Improvements in the copper method for estimating amino acids, P. A. 

 KoBER (Jour. Indus, and Engin. Chem., 9 (1917), No. 5, pp. 501-504. figs. 2). — 

 Simple methods for dehydrating and weighing copper sulphate for use in mak- 

 ing standard solutions, keeping a saturated solution of potassium iodid con- 

 taining starch and acetic acid, and making a permanent suspension of cupric 

 hydroxid are described in detail. A concise description of the procedure for 

 amino acid determination by the copper method is included. 



A simplified inversion process for the determination of sucrose by double 

 polarization, H. S. Walkkr (Jour. Indux. and En/fin. Chrm., 9 (1917). No. 5. 



