18 PROTEIDS. 



3. Alkali-albumin. 



- or_egg-albumin or washed muscle be tteafed with 

 dilute alkali instead of with dilute acid, thejroteid undergoes"^ 

 change in many ways similar tci-tbat which was brought about by 

 the acicT The alkaline solution, when the change has become 

 complete, is no longer p.nn|rn1nt,p.d by heat, the proteid is wholly 

 precipitated on neutralisation, and the_ precipitate^ insoluble in 

 water and in_jieutral solutions of sodiimicHiToride, is readily solu- 

 ble in dilute acids or alkalis. 



Alkali-albumin may be prepared by the action not only of 

 dilute alkalis but also of strong caustic alkalis on native albumins 

 as well as on coagulated albumin and other proteids. The jelly 

 produced by the action of caustic potash on white of egg (p. 11) 

 is alkali-albumin ; the similar jelly produced by strong acetic acid 

 is acid-albumin. 



In short, the general statement may be made that under other- 

 wise similar conditions, if an alkali is employed instead of an 

 acid to act on proteids. alkali-albumin is formed instgadjof acid- 

 ajbumin! In the opinion of many authors 1 th precipitates ob- 

 tained by neutralising the acid or alkaline solutions which arise 

 djiring the preparation of acid- and alkali-albumin respp-f-tivp.1v 

 are to be regarded as identically the same. According to this 

 view the neutralisation precipitate is itself neither acid- nor alkali- 

 albumin, but becomes either the one or the other by solution in 

 either an acid or alkali, entering at the same time into union with 

 the acid or alkali. 



Danilewsky 2 has utilised the tropaeolins for the purpose of deter- 

 mining the fixation of acids or alkalis by proteids, and on this he has 

 based a classification of these substances. The tropaeolins are soluble 

 in water, the one (tropaeolin 00) yielding a yellow, the other (tro- 

 paeolin OOO No. 1) an orange solution. The first is changed to a 

 lilac colour by acids, but not by salts which have an acid reaction to 

 litmus. The second is turned to bright carmine by free alkalis, but 

 not by salts which have an alkaline reaction to litmus. 



It is however on the whole more prnbnhlp 3 that acid- and 

 alkali-albumin are distinct, though very closely allied substances, 

 and we might go even so far as to say that probably every proteid 

 yields its own kind of either the one or the othp.r prntp.i'H on t.rp.at- 



B "^^HMMBIMaMV^MM^^HHHMMMMMHM^V>MMMi^MMBHHBMM^HH^M M ^l^ M _ M ^^^^MWKV"l*^ 



ment with acids and alkalis. But as yet we do not possess any 

 means of distinguishing between the several forms of each sub- 

 stance by any ordinary reactions. 



1 Soyka, Pfluger's Arch. xii. (1876), S. 347. 



2 Centralb.f. d. med. Wiss. 1880, No. 51. 



3 Morner, Pfluger's Arch. Bd. xvn. (1878), S. 468. But see also Kieserit/.ky. 

 Inaug.-Diss., Dorpat, 1882. Abstr. in Maly's Jahreslter. Bd. xn: (1882), S. 6, and 

 Rosenberg, Inaug.-Diss., Dorpat, 1883. Abstr. in Maly, Bd. xm. (1883), S. 19. 



