206 EXPERIMENT STATION KECORD. 



Tbescot {Jour. Indus, and Engin. Chem., 5 {1913), No. 11, pp. 914, 915). — This 

 is a comparative study of the Gimning-Kjeldahl and Kjeldahl-Gunning-Arnold 

 methods for nitrogen. The materials studied were hair waste, dried blood, bone 

 meal, leather, leather waste, cotton-seed meal, linseed meal, gelatin, cyanamid, 

 beef extract, desiccated meat, flour, bread, gluten bread, macaroni, ground rye 

 hay, shorts, bran, molasses feed, milk, condensed and evaporated milk, and 

 cheese. 



The conclusion reached from the results is " that the Kjeldahl-Gunning- 

 Arnold method with 1* hours' oxidation, except in the case of cyanamid, which 

 requires 2i hours, gives more concordant and reliable estimation of nitrogen 

 than do the official Gunning or official Kjeldahl methods, both of which re- 

 quire from 3 to 4 hours for oxidation, depending upon the matei'ial." 



The aluminum reduction method as applied to the determination of ni- 

 trates in "alkali" soils, P. S. BrROESs (TJniv. Cal. Pubs. Agr. Sci., 1 {1913), 

 No. Jf, pp. 51-62, fig. 1). — In this paper the following points are emphasized: 



" The aluminum reduction method <^ for the determination of nitrates in soils 

 yields the most accurate results of all methods now commonly in vogue. Alkali 

 salts do not in any way interfere with the successful operation of the method. 

 The presence of extraordinarily large amounts of soluble organic materials (sol- 

 uble humus and dextrose) have little effect on the method, 



"A temperature of 20° C. for from 11 to 15 hours has been fouud the optimum 

 for the reduction of large quantities of nitrates. The proper amount of NaOH 

 to be employed in the reduction was found to be 2 cc. of a 50 per cent solution, 

 with an aluminum strip weighing approximately 1 gm." 



Mineralogical soil analysis, W. J. McCaughey {Jour. Indus, and Engin. 

 Chem., 5 {1913), No. 7, pp. 562-564)- — IQ this paper it is pointed out that the 

 mineralogical analyses of soils are not usually made from the standpoint of 

 the soil investigator. The value of such analyses is shown by numerous 

 examples. 



Determination of manganese in the soil, M. J. Steitak {Ztschr. Analyt. 

 Chem., 52 {1913), No. 6, pp. 337-345). — For soils containing a medium amount 

 of calcium, the following method is proposed : 



An extract is first made by treating 100 gm. of the soil with 25 per cent hydro- 

 chloric acid for 2 hours at 100° C. and then making up to 500 cc. Fifty cc. 

 of this extract, is placed in a 200 cc. Kjeldahl flask with 25 cc. of concentrated 

 nitric acid (preferably fuming). This is concentrated as far as possible by 

 slow boiling, transferred to a porcelain dish, and evaporated to sirupy con- 

 sistency on a sand or water bath. From 10 to 20 cc. of concentrated nitric 

 acid is added to the residue and evaporated, this operation being repeated 3 

 successive times. The residue is then transferred with dilute nitric acid and 

 water to a 100 cc. flask, cooled, and 1 to 2 drops of a sulphocyanid solution 

 added (and when necessary 2 cc. of iron-alum solution) until a definite red 

 coloration is present. The color is discharged with tenth-normal silver nitrate 

 solution and restoi'ed with sulphocyanid solution. The solution is heated 

 slightly, cooled, filled to the 100 cc. mark, and filtered. 



Next, 25 cc. of the filtrate (free of chlorin and silver ions) is mixed with 

 17 cc. of nitric acid, cooled to 17 to 1S°. shaken for 15 minutes with from 1 to 

 1.2 gm. of bismuth peroxid. cooled for from 2 to 3 minutes with cold water, 

 filtered through an asbestos filter tube containing a porcelain filter disk into 

 a 250 cc. flask, and the residue washed on the filter with cold water. The 

 colored solution is then rapidly oxidized with about tenth-normal hydrogen 

 peroxid solution and brought to a pink tint by the addition of tenth-normal 

 potassium permanganate solution. 



'Amcr. Jour. Pub. Hyg., 19 (1909), No. 3, pp. 536-544. 



