REPORT OF THE DEPARTMENT OF 

 CHEMISTRY. 



PREPARATION, COMPOSITION AND PROPER- 

 TIES OF CASEINATES OF MAGNESIUM.* 



L. L. VAN SLYKE and O. B. WINTER. 



SUMMARY. 



1. Preparation of solution of casein in magnesium hydroxide. — In 

 preparing magnesium caseinates, the solution of casein in magne- 

 sium hydroxide is effected by suspending pure casein in water with 

 an excess of finely-divided magnesium oxide, allowing the mixture 

 to stand several days with occasional agitation. 



2. Preparation and composition of basic magnesium casemate. — 

 The magnesium hydroxide solution of casein is made neutral to 

 phenolphthalein with HC1 and the solution dialyzed and evaporated 

 to dryness. The preparation contains 1.06 per ct. Mg (1.76 MgO), 

 the theoretical composition being 1.09 per ct. Mg (1.81 MgO); or 

 1 gram of casein combines with 8.7 x io>- 4 gram equivalents of Mg 

 (theoretical, 9.0 x 10- 4 ). The compound is easily soluble in water 

 and in a 5 per ct. solution of NaCl. 



3. Preparation and composition of neutral magnesium caseinate. — 

 The magnesium hydroxide solution is made neutral to litmus with 

 HC1 and the solution dialyzed and the caseinate precipitated with 

 alcohol. The preparation contains 0.71 per ct. Mg (1.18 MgO), the 

 theoretical composition being 0.67 per ct. Mg (1.12 MgO); or 1 gram 

 of casein combines with 5.8 x 10- 4 gram equivalents of Mg (theo- 

 retical, 5.6 x 10- 4 ). The compound is easily soluble in water and 

 in a 5 per ct. solution of NaCL 



4. Preparation and composition of mono-magnesium caseinate. — ■ 

 A solution of base-free casein in magnesium hydroxide is treated 

 with HO just to the first point of precipitation and then dialyzed. 

 Alternate addition of acid and dialysis are repeated, until finally the 

 dialyzed solution forms a permanent precipitate on the addition of 

 any acid. To this solution is added one-third of the amount of acid 

 required for complete precipitation of the casein, the solution filtered 

 and dialyzed and divided into two portions. One portion is used 

 for the preparation of mono-magnesium caseinate by incomplete 

 precipitation with HC1. The preparation contains 0.13 per ct. Mg 

 (0.22 MgO), which is the theoretical composition; or 1 gram of casein 

 combines with r.r x ro- 4 gram equivalents of Mg. This compound 

 is insoluble in water but soluble in 5 per ct. solution of NaCl; at 

 65 C. it tends to form strings when drawn out. 



* Reprint of Technical Bulletin No. 3.3, February. 



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