AGRICULTURAL CHEMISTRY. 831 



sample of air can be calculated from the time during which the current has 

 passed and the amount of gas absorbed, a correction being applied for the 

 effecl of change of temperature on the rate of absorption. 



On the determination of carbon monoxid in the air by means of iodin 

 anhybrid, Ai.kikt-Li' \ v and A. Pecoul (Compt. i:< nd. lead. 8ci. [Paris], 1 ) : 

 i 1906), Vo. 8, />. Hi'; abs. in Rev. Sci. [Paris], ■',. ser., ■', { 1906), So. ). //. 112). 

 In the aiethod proposed use is made of the fad thai one pari of carbon monoxid 

 in 10,000,000 of air gives an intense coloration in chloroform containing the 

 anhydrid .-is ,-i result of the liberation of iodin. Acetylene of the same strength 

 gives no coloration. 



The determination of sulphuric acid in drinking water, F. EiASCHIC 

 {Ztschr. Angeiv. Chem., t9 (1906), \ o. S, />. 834). '" the method proposed j 

 liter to ."i liters of water, according to the sulphuric acid content, is mixed witli 

 the twentieth pari of its volume of concentrated benzidin solution, stirred, and 

 allowed to stand 15 minutes, if no precipitate is formed, the water contains 

 1.5 mg. of sulphuric acid (SO a ) or less. If a precipitate forms, it is collected on 

 a filter, washed, and titrated in the usual way with tenth-normal sodium 

 bydroxid. one cc. of the hydroxid corresponds to I mg. of s< > , A correction 

 of 1.5 mg. nmst be added in each determination. 



Field assay of water, M. ( >. Leighton </. 8. Oeol. Survey, Water-Supply 

 and Irrig. Paper So. tol, m>. 77. pis. /. figs. 3). — This paper describes and dis- 

 cusses methods which have for seme time been successfully used in investiga- 

 tions carried en by the division of hydro-economics of the {]. s. Geological 

 Survey en the quality of water in various parts of the United States. 



Methods of determining turbidity, color, total hardness, alkalinity, normal 

 carbonates, bicarbonates, total sulphates, chlorin, or total chlorids, iron, and 

 calcium are discussed. Only such methods are described as are considered 

 necessary for the determination of the ingredients which give waters their 

 essential characteristics, and these are confined to simple and cheap methods 

 useful for practical purposes and easily carried out in the field, hut of little or 

 no value from a purely scientific standpoint. 



On the theory of the formation of potash deposits from sea water, E. 

 Janecke (Ztschr. Angew. Chem., n> (1906), Vo. /. i>i>. 7-/}. figs. 8). — A discus- 

 sion of the physico-chemical theory of the formation of oceanic salt deposits ;is 

 enunciated by Van'1 Hoff. 



Colorimetric, turbidity, and titration methods used in soil investigations, 

 ( '. S< hbeiner and <;. 11. Failyeb (U. S. Dept. Agr., Hit. soils linl. .11. \>\>. i;<>. 

 ///. /. figs. 5 ). —The methods which have hcen used in the investigations of the 

 Bureau Of Soils and others which are applicable to similar work are concisely 

 described in this bulletin "for the convenience of those desirous of continuing 

 these Investigations or of carrying on new lines of inquiry." 



After a preliminary explanation of methods of preparing solutions from 

 moist and dry soils, the construction and operation of the Briggs filtering 

 apparatus (E. s. K.. 14, p. 126), the decolorizing of soil solutions, the use of 

 centrifugal and other methods of obtaining soil solutions devised by Briggs, 

 McLane, and McCall (1-:. S. K.. 1»;. p. 450), the preparation and decolorization of 

 solutions from green and dried plants, the general principles and purposes of 

 colorimetric. turbidity, and titration methods, and the construction and use of 

 colorimeters, especially that of Schreiner, the authors describe in detail the 

 following methods: Colorimetric methods — ammonium. Nessler; potassium, 

 Cameron and Failver (E. S. It.. IT,, p. 111. and Hill (E. S. R., 15, p. 224): 



" Jour. Amer. Chem. Soc., 27 (1905), pp. 1192-1203. 



275S8— No. 9—06 2 



