New York Agricultukal Experimext Station. 315 



cotton. The casein is then precipitated again with dilute acetic 

 acid; the precipitate is allowed to settle, and is then washed, redis- 

 solved in dilute ammonium hydroxide, and filtered, the process of 

 precipitation, washing, dissolving, etc., being repeated not less than 

 four times. Finally an excess of strong ammonium hydroxide 

 (10 cc.) is added and then 20 cc. of saturated solution of ammonium 

 oxalate. The mixture is allowed to stand 12 hours or more. Cal- 

 cium is precipitated as oxalate in very finely divided condition, too 

 fine to permit its satisfactory removal by ordinary methods of fil- 

 tration. Better aggregation of the precipitate can, however, be 

 effected by means of centrifugal force. The centrifuged mixture is 

 then filtered through double thickness of filter paper. The filtered 

 solution is next treated with dilute hydrochloric acid (10 cc. of HCl, 

 sp. gr. 1 . 20, diluted to 1 liter) until the casein is precipitated. The 

 precipitate is washed with distilled water until free from chloride 

 and is then placed on a hardened filter paper in a Buchner funnel, 

 as much water as possible being now removed from the precipitate 

 by suction. The mass is next transferred to a large mortar and 

 thoroughly triturated with 95 per ct. alcohol. The alcohol is then 

 removed by suction on a Buchner funnel and the casein is then 

 again placed in a mortar and triturated with absolute alcohol. Most 

 of the alcohol is removed by filtration and the casein treated twice 

 with ether in a mortar by trituration, the ether being removed each 

 time by means of suction on a Buchner funnel. The material is 

 then placed in a large evaporating dish and spread out in a layer as 

 thin as possible; it is allowed to stand 12 hours or more in a warm 

 place; and is finally ground in a mortar until the particles pass a 

 40-mesh sieve, and is dried two days over sulphuric acid in a 

 desiccator under diminished pressure. 



Three preparations made in this way were found to show an ash 

 content of 0.10, 0.09 and 0.06 per ct., respectively. These prepa- 

 rations were insoluble in water and in 50 per ct. alcohol; the first 

 one was very slightly soluble in a 5 per ct. solution of sodium chloride, 

 but the two others were not. 



When one gram of these casein preparations was treated with 

 10 cc. of Yo hydroxide of ammonium, sodium or potassium, and 

 90 cc. of water, a clear solution was obtained, the casein dissolving 

 completely. When to this solution a minute amount of a solution 

 of a barium, calcium or strontium salt was added, there developed 

 promptly the opalescent appearance characteristic of casein solutions 

 under such conditions. 



Casein prepared in the mamier described was analyzed, with the 

 following results: 



Per ct. Per ct. 



Moisture 1 . 09 In dry substance: 



In dry substance: Nitrogen 15 . 80 



Ash 0.06 Phosphorus 0.71 



Carbon 53.50 Sulphur 0.72 



Hydrogen 7. 18 Oxygen (by difference) 22.08 



