112 EXPERIMENT STATION RECORD. [Vol. 3S 



with the soil, filtering through the Chamberland-Pasteur filter, or by cen- 

 trifugalization. When alum is used no other antiseptic is necessary, but unless 

 the analysis is to be completed at once 0.5 cc. of chloroform should be added 

 to each sample. 



An aliquot part (100 cc.) of the supernatant liquid is evaporated with 2 cc. 

 of a saturated solution of sodium hydroxid to about one-fourth its original 

 volume, and if urea is present, to dryness. The neck of the reduction flask is 

 fitted with a two-hole stopper through which passes a 50-cc. separatory funnel 

 and a bent tube which dips into a vessel containing water to prevent mechanical 

 loss. The residue is transferred to the reduction flask with 50 cc. of ammonia- 

 free water and 5 gm. of " iron-by-hydrogen " and 30 cc. of sulphuric acid 

 ( specific gravity 1.35) then added. The acid should be slowly added and 

 allowed to stand until the rapid evolution of hydrogen is over and then heated 

 to boiling for 10 minutes. The contents of the side vessel should be returned 

 to the reduction flask before the reaction is complete to insure the complete 

 reduction of any nitrates which may have been carried over with the first 

 violent evolution of hydrogen. When the reduction is completed the contents 

 of the flask are transferred to a Kjeldahl flask, neutralized with sodium 

 hydroxid, and distilled into standard acid. The excess of acid is titrated back 

 with standard alkali, and lacmoid used as the indicator. Proper checks should 

 be made on all reagents, including the alum used as a flocculent. 



A bibliography of 58 references to the literature cited is appended. 



Note on the Blacher method for the determination of hardness in water, 

 A. D. Behbman {Philippine Jour. Sci., Sect. A, 11 {1916), No. 6, pp. 291-293).— 

 The author briefly notes the results obtained in a study of the effect of free 

 carbon dioxid, removal of carbon dioxid, effect of sodium chlorid, and the effect 

 of dilution of very hard water on the determination of hardness by the Blacher 

 method (E. S. R., 31, p. 502). 



A modified procedure for the determination of hardness in water based on 

 the data obtained in the above study is outlined. 



A rapid volumetric method for the approximate estimation of chlorin in 

 milk, B. W. Hammek and D. E. Bailey {Iowa Sta. Research Bvl. Ifl {1917), pp. 

 537-3^8). — The relation of high chlorin content to abnormal flavors and odors 

 of milk and the literature pertaining thereto are briefly discussed. 



In the study reported data were obtained by direct titration of the chlorin 

 in milk with silver nitrate, using potassium chromate as indicator, and by de- 

 termining the chlorin in the ash by the Volhard method. Consistently higher 

 results were obtained on 49 samples of milk by the direct titration method than 

 by the ashing method. Examination of the differences between the results ob- 

 tained by the two methods indicates that the direct titration of milk with 

 standard silver nitrate gives a satisfactory comparative index of the chlorin 

 content of the sample. By subtracting 0.025 per cent from the results obtained 

 in the direct titration procedure, results approximating those secured by the 

 ashing method are obtained. The direct titration procedure outlined is as 

 follows : 



A 5-cc. sample of milk is placed in a porcelain dish with 50 cc. of distilled 

 water and 1 cc. of a 10 per cent potassium chromate solution. The standard 

 silver nitrate solution is added with stirring until there is a distinct change in 

 color. The solution used was made so that 1 cc. equaled 0.01 per cent chlorin 

 and contained 2.4722 gm. of silver nitrate per liter. 



The chlorin content of the samples examined by the ashing method varied 

 from 0.0504 to 0.194 per cent and averaged 0.0968 per cent. In an attempt to 

 determine whether the phosphates, the fat, or the casein were responsible for 



