252 



As to the time required for the action to complete itself, the same 

 results were obtained after a few minutes and after several days, show- 

 ing that the equilibrium is very quickly established. 



A similar series of experiments carried out with potassium chloride 

 and filter paper gave analogous results, the adsorption, however, beginning 

 at twentieth-normal, and only rising to something over 5 per cent, of that 

 present at five-hundredth-normal concentration. 



The work is being continued and promises further interesting results. 



The Determination of Manganese in Iron and Steel. 

 W. A. NoYES AND G. H. Clay. 



The process proposed involves no new principle, but is a combination 

 of several old methods. 



REAGENTS. 



Ferrous (unmonhim siilphdte. — Dissolve 8.56 g. Crystallized ferrous am- 

 monium sulphate in water containing 40 cc. of dilute sulphuric acid (2.5 per 

 cent.) and make up to one liter. 



Potassium permatrgandtr.—A standard solution of such strength that 1 cc. 

 is equivalent to about 0.001 g. Fe. The manganese equivalent for the pres- 

 ent method is foimd by multiplying the iron equivalent by ff^ 



Sodium acetate.— Thirty grams of crystallized sodium acetate, £0 cc. of 

 acetic acid' (30 per cent.) and 170 cc. of water. 



Bromine water.— A saturated solution. 



TROCESS. 



Dissolve 1.5 grams of the sample in 20 cc. of nitric acid (1.20) and 5 cc. 

 of hydrochloric acid (1.12). Heat till dissolved, transfer to a 300 cc. flask, 

 add a solution of sodium carbonate till nearly neuti'al and then zinc oxide 

 slowly till the precipitate of ferric hydroxide forms. After two minutes 

 add an excess of zinc oxide. 



Make up the volume to 300 cc. mix by pouring back and forth into a 

 dry beaker and filter througli a dry filter. Take 200 cc. of the filtrate, 

 add 20 cc. of the sodium acetate solution and 40 cc. of bromine water.. 



