110 EXPERIMENT STATION EECOED. 



According to the author, Caro's method yields low results. A sample of 

 newly made calcium cyanamid on analysis yielded the following : " Total nitro- 

 gen by the salicylic acid method, 21.5 per cent ; nitrogen, by the usual Kjeldahl 

 process, 20.5; nitx'ogen, as cyanamid, by the above method, 18.98 per cent." 



A study of the phenolsulphonic acid method for the determination of 

 nitrates in water. — A modified phenolsulphonic acid method, E. M, Chamot, 

 D. S. Pkatt and H. ^Y. Eedfield (Jour. Amei: Chem. Soc, 33 {1911), No. 3, pp. 

 381-38'f). — After trying several methods for preparing the phenolsulphonic acid 

 reagent, the authors suggest the following : " Dissolve 25 gm. of pure white 

 phenol in 150 cc. of pure concentrated sulphuric acid, and 75 cc. of fuming sul- 

 phuric acid (13 per cent SOa), stir well, and heat for 2 hours at about 100°." 

 They state that the reagent thus prepared contained no mono or tri acids. 



In determining nitrates it is necessary to determine first the chlorin and 

 nitrite content and the color, then " measure into an evaporator 100 cc. of the 

 sample, or if the nitrates are very high, such a volume as will contain about 

 10 parts per million of nitric nitrogen, faii'ly low colorimeter readings having 

 been found most I'eliable. Add sufBcient ^V normal or ^V normal sulphuric acid 

 to not quite neutralize all the alkalinity, then a volume of standard solution 

 of silver sulphate free from nitrate (4.3969 gm. per liter, 1 cc.=l cc. of standard 

 silver nitrate solution=l mg. CI per cc), which will precipitate all but about 

 0.5 mg. of the chlorin. Heat to boiling, add a little ' aluminum cream,' filter, 

 and wash with small amounts of hot water. Evaporate the filtrates to di"yness, 

 add 2 cc. of the disulphonic acid reagent, rubbing with a glass rod to insure 

 intimate contact. Should the residue be compact or vitreous in appearance 

 from much magnesium or much iron present, place the evaporator on the water 

 bath for a few minutes. Dilute with distilled water and add slowly a strong 

 solution of potassium hydroxid (10 to 12 normal) until the maximum color is 

 developed. Transfer to a colorimeter cylinder, filtering if necessary, and com- 

 pare with a potassium nitrate or tripotassium nitrophenoldisulphonate standard." 



If nitrites are present in excess of 1 part per million of nitrogen a slight 

 error is introduced, which may be removed by heating the sample under exami- 

 nation a few minutes with a few drops of hydrogen peroxid free from nitrates, 

 or adding a dilute solution of potassium permanganate in the cold until a pink 

 tint appears. A correction is then applied to the final nitrate determination,' 



The authors present some notes on the preparation of tripotassium nitro- 

 phenoldisulphonate for preparing colorimetric standards. 



Volhard's method for the estimation of chlorin in potable waters, A. T. 

 Stuart (Jour. Amer. Clicm. Soc, 33 {1911), No. S, pp. 13U-13^9, figs. 2).— 

 The method when used for drinking water where the chromate method is inap- 

 plicable, as for instance in peaty waters, can only be used when a very small 

 excess of silver nitrate solution is added, not greater than 0.2 cc. (1 cc.= 

 0.001 gm. CI). The plus or minus error for water containing about 10 parts 

 per million of chlorin will be within 0.5 part per million. Aqueous solutions 

 containing more than the ordinary concentrations of chlorin showed quite a 

 noticeable variation, which, however, was not serious enough to interfere with 

 the practicability of tlie method. 



Suggestions on micro-analytical methods for the examination of drugs, 

 foods, and spices. A, Schneider {Merck's Rpt., 20 {1911), Nos. 2, pp. 33-35; If, 

 pp. 91-93; 6, pp. 159-161, figs. 3). — This is a detailed description of micro- 

 scopical methods. 



The examination of turtle meat for adulteration, F. Yoshinaga {Munchen. 

 Med. Wchnsclir., 56 {1909), No. 1/9, p. 2526; ahs. in Berlin. Tierdrztl. Wchnschr., 

 26 {1910), No. 5, p. 118). — The author was able to determine by the precipitin 



