208 



EXPERIMENT STATION EECORD. 



fereuce with the function of tlie oxygen, while such conspicuous oxidizing 

 agents as chromic acid and its soluhle salts, by inducing a passive condition, 

 interfere with the action of the hydrogen ions." 



The etiiciency of preserving iron by coating it with different substances is 

 discussetl. Samples of wire coated with zinc by various processes have been 

 put up in the form of a fence to test tlie inhibitive effect of zinc, and other 

 materials are also under test. Laboratory tests were undertaken by different 

 investigators to ascertain the value of pigments as rust inhibitors, and from 

 their results a tentative classification of the pigments is proposed in the follow- 

 ing table: 



Classipratidn of jiUjinrnis. 



" If we apply the autoelectrolytic theory of the cause of corrosion to the sub- 

 ject of protection by paint films, it follows that in general pigments that are 

 good conductors of electricity should never be applied directly to the surface 

 of iron or steel." 



Acceleration tests of a number of pigments made with water according to a 

 simple method described in detail were found to agree with the oil-film test pre- 

 viously used. 



It is pointed out that the protection of a metal which from the nature of its 

 service can not be treated with a protective coating is purely a metallurgic 

 problem to be solved by the manufacture of a perfectly homogeneous and care- 

 fully worked material. " If anyone should discover a method for applying a 

 skin of high silicon metal on worked steel it would be a contribution of the 

 highest value to the art of metallurgy and to the world at large." 



A' method for the quantitative determination of nitrogen in very small 

 amounts, E. A. Mitscherlich, P. Herz, and E. Merres {Landiv. Jahrh., 38 

 {1909), No. 2, pp. 279-3JS, figs. 2; Lanclw. Vers. Stat., 70 (tOO'J). No. 5-6, pp. 

 J,05-Jfll, figs. 2; abs. in Chcm. ZentN., 1009, I, No. l',, pp. 1195, 1196).— The 

 method proposed by the author.s, which is adapted especially to the determina- 

 tion of small amounts of nitrogen as in bacteriological investigations, is in brief 

 as follows: 



To the solution containing from o to 10 mg. of nitrogen in a K.jeldahl fiask 

 add 3 gm. of Devarda's reagent. 'Connect with a Hugershoff distillation appa- 

 ratus, add 50 cc. of concentrated sodium hydrate and distill into 10 cc. of nor- 

 mal sulphuric acid, then add 50 cc. of water and 60 cc. of concentrated sul- 

 phuric acid to the Kjeldahl flask, and heat until the mass becomes blue. To 

 the distillate obtained add zinc filings and distill after adding 120 cc. of con- 

 centrated sodium hydrate, collecting the distillate in tiftieth-uormal sulphuric 



