10 EXPEEIMENT STATION RECORD. 



pounds formed by casein and paracasein with bases, especially with calcium, 

 and particularly to determine whether there were other compounds containing 

 less calcium than the compounds previously prepared by the authors (E. S. R., 

 16, p. 1018), and to ascertain the composition of the substances formed in 

 cheese which are soluble in 5 per cent sodium chlorid solution (E. S. R., 26, 

 p. 212). 



It is pointed out that for investigations of this sort casein must be made 

 base-free. " Preparations were made containing less than 0.1 per cent of ash. 

 The usual method was employed in part, precipitating separator skim milk 

 with dilute acetic acid, redissolving the washed precipitate in dilute NH2OH, 

 and continuing pi*ecipitation and solution 3 or more times. Finally, the remain- 

 ing calcium is precipitated from the ammonia solution as oxalate, the precipi- 

 tate being removed by centrifuging and filtering, and the filtrate precipitated 

 with dilute HCl. After washing free from HCl, the casein is treated with 

 alcohol and ether, and after grinding and partial drying is dried over H2SO1 

 under reduced pressure. Analysis of such casein preparations agrees with the 

 composition generally accepted, except in the amount of phosphorus and 

 sulphur." 



Basic calcium caseinate " was prepared in two ways, (1) by decomposing CaCOj 

 with casein, and (2) by treating casein with a lime water solution and neutral- 

 izing the excess with HCl with phenolphthalein as indicator. The composition 

 of the resulting compound was determined (1) by weighing the CO2 expelled 

 from CaCOs, (2) by determining the Ca in the resulting casein compound, and 

 (3) by analysis of the compound formed by treating lime water solution of 

 casein with acid until neutral to phenolphthalein. The different results agree 

 closely, showing basic calcium caseinate to contain about 1.78 per cent Ca (2.5 

 CaO), or 1 gm. of casein combines with 9X10—* gm. equivalents of Ca." 



To prepare acid or unsaturated caseinates of ammonium, sodium, and potas- 

 sium, " ash-free casein is dissolved in alkali so that 50 cc. of fiftieth-normal 

 alkali contain 1 gm. of casein. This is neutralized with fiftieth-normal HCl, 

 which is added in small portions, under constant agitation, until a permanent 

 precipitate begins to appear, as shown by centrifuglng a portion of the mixture 

 in a sedimentation tube. This method enables one to detect the casein precipi- 

 tated by 0.2 cc. of fiftieth-normal HCl. The point at which a permanent 

 precipitate first begins to appear is noted, and addition of acid is continued 

 imtil all the casein is precipitated, which point is also noted. Three different 

 casein preparations were used and numerous determinations were made. It 

 was found that 1 gm. of casein forms a soluble compound with each of the 

 alkalis used when combined with amounts somewhere between 1.1X10— ■* and 

 1.15X10—^ gm. equivalents of alkali; or, 1 cc. of tenth-normal alkali combines 

 with an amount of casein somewhere between 0.87 and 0.91 gm. The propor- 

 tion of basic element in each compound is as follows : NH4, 0.2 per cent ; Na, 

 0.26 per cent ; and K, 0.44 per cent. Such casein compounds contain the smallest 

 known amount of base, and it is suggested that they be called monobasic 

 caseinates." 



In preparing acid or unsaturated caseinates of calcium, strontium, and 

 barium 1 gm. of ash-free casein is dissolved in 250 cc. of fiftieth-normal 

 hydroxid solution, and fiftieth-normal HCl is added until the first sign of a 

 permanent precipitate appears, as shown by centrifuglng a portion. The solu- 

 tion is then dialyzed to remove soluble chlorid, and then acid is again added 

 until precipitation again occurs and another dialysis is made. Alternate 

 addition of acid and dialysis are continued until finally the dialyzed solution 

 forms a permanent precipitate with the addition of any acid. The results of 

 many experiments agree in indicating the formation of two sets of compounds. 



