CHEMICAL I!A>IS <F Till: ANIMAL HoDV. L'l 



substam (4 6 tfrin.) leaves scarcely a tract- of ash. h i- prac- 

 ticiillv insoluble in water, but is soluble in alkalis, carbonates and 

 phosphates (if the alkalis, lime- and baryta-water. From the-.- 

 solutions it inav In- precipitated by excess of neutral salts such as 

 sodium chloride. anoMjy dilute acids, in which it is a^ai'n soluble 

 ifatiy^x^ss ^ ac *^ ls prcs^rct- Its reactions thus correspond 

 closely to those of acid- and alkali-albumin, but as will be 

 ently shewn it is in many ways perfectly distinct from these 

 substances. Solutions of pure c.ist'in an- in )t cna^ulatrd liy l.oil- 

 inu f , but if heated to 130 loQ" in sealed tubes a coagulation is 

 obtained. 



\Vln-n ;u-iil> arc aildfd t diluted milk l<> effect the jtrecijiitat i.n of 

 .;i-.-iii IK. precipitate is obtained until the >nluti(in ha- a di-tinetly 

 acid react inn; this has usually l>cen att riluited to the pre>eiic.- in milk 

 <f potassium phosphate. ' Hanniiarsten has houi-vn- shewn - that the 

 .-ame hidils ^ ..... 1 for solution- of ca-ein free fr..m thi> -alt. 



When jin-jiiired from milk by magnesium snljihate (see below), 

 freed by ether from fats, and dissolved in water, casein possesses 

 a specific rotatory power (0)0= 80; in dilute alkaline solu- 

 tions. of -76; in strong alkaline solutions, of -91; in 

 dilute solutions, of - 87. 3 



Although purified casein leaves no ash-residue on ignition. Ham- 

 in, trsten found that it contained a m/ixtnnt and fairly laiye amount 

 of phosphorus, as a mean -S47 ]>.c. From this fact and its be- 

 haviour towards sodium chloride in dilute solution-, he r-_;ards 

 ca-ein as bein^ a nucleo-albumin 4 (see below). This viev. 

 iv-ponds with the ie-ult- previously obtained by I.ubavin/' who 

 found that a pho.-phorised ( nuclein ) constituent of . a-.-m is sep- 

 1 out a- an insoluble residue during the digestion of i-a-ein 

 with gastric juice. 



\_i_t the vii-ws of inaiiv authors milk <'oiituin.s HQ - 

 oidv. lnit at least two forms of |U-otei(l u hirh pass under the ojie 

 I lainiiiar.-teii 7 has criticised these views and conclude- that 

 ii is a unitary substance, and not a mixture i.r compound 



A, tm, i j ,-,,111111 nn eatrin. This ha- b,-, n fully studied by 

 Hainmar-teii. \\bo-. iv-ults may be summaiised a- folio, 



' Kiilnu-. /../ir'.. tl.,.h,,l. &**. I-' 



kUlr'i /;, ,. MI B 



Hoppe-Serler, //-///,. (K-i. r.) p 286. 



Hoppe-Seylcr'H ./.'/../!... ('ntmnch. Ilf M 3. 



Mill.,,, ' ( . .nun ail!.-. / 



Maly 

 IM v 



