CHAP. II.] THE BLOOD. 63 



tated by mineral acids, and especially by nitric acid; they are like- 

 wise precipitated by tannic acid and by metaphosphoric acid. 



When heated to 60C. solutions of serum-albumin usually become 

 opalescent, and at temperatures between 72 75 the albumin 

 separates in a flocculent form. Solutions of albumin which have 

 been long dialysed, but are not free from salts, are exceptions 

 to these statements. (See Schmidt's and Aronstein's pure albumin.) 



Most metallic salts, such as mercuric chloride, copper sulphate, 

 lead acetate, at once precipitate ordinary serum-albumin. 



Ether does not precipitate serum-albumin, whilst it does precipi- 

 tate 



Schmidt's and Aronstein's pure serum-albumin and its reactions. 



It was asserted by Graham 1 tliat by mixing egg-albumin with acetic 

 acid and placing the mixture in a dialyser, all the acid, together with the 

 alkaline and earthy salts, diffused out, leaving the albumin pure, so that the 

 dried substance, on being ignited, left no ash. This albumin was found 

 by Graham to have a slightly acid reaction. Kiihne and Hoppe-Seyler were 

 unable to confirm the statement of Graham. 



Arotistein 2 , working under the direction of A. Schmidt, asserted that 

 if serum be subjected to long continued dialysis, the whole of the para- 

 globulin is precipitated and the whole of the salts are removed from 

 the albumin, which when burned leaves no ash. He asserted that such 

 albumin when dissolved in water is not coagulated by boiling, and is not 

 precipitated by alcohol. The addition of small quantities of common salt 

 leads, according to Aronstein, to the albumin being again coagulable 

 by heat and by alcohol. These observations of Aronstein received the 

 full confirmation of A. Schmidt 3 , who, in addition, asserted that dilute 

 solutions of pure albumin, obtained by dialysis, gave no precipitate with 

 copper and zinc sulphate, with neutral lead acetate, with mercuric chloride 

 and many other salts which precipitate ordinary albumin. Platinum 

 tetrachloride, nitric acid, tannic acid, ferrocyanide of potassium and acetic 

 acid, were stated to be the reagents which most easily precipitate pure 

 albumin from its solutions. 



The observations of Aronstein and Schmidt have not however been 

 confirmed. 



Heynsius 4 found it impossible to obtain any serum-albumin (by 

 Aronstein and Schmidt's process) free from ash, and attributed the non- 

 coagulation. in Aronstein's experiments to the presence of a slight alkaline 

 residue. Similarly Winogradoff 5 repeating Aronstein and Schmidt's 



1 Graham, " Liquid diffusion applied to analysis." Philosoph. Transact., 1861. 



2 Aronstein, " Ueber die Darstellung salzfreier Album inlosungen vermittelst der 

 Diffusion." Pfliiger's Archiv, 1873, Vol. vm. p. 75. 



3 A. Schmidt : " Untersuchung des Eiereiweisses und Blutserums durch Dialyse." 

 Ludwig's Festgabe, 1874, pp. 94115. "Weitere Untersuchungen des Blutserums, 

 Eiereiweisses und der Milch durch Dialyse mittelst geleimten Papiers," Pfliiger's Archiv, 

 Vol. ii. pp. 152. 



4 Heynsius, " Ueber die Eiweissverbindungen des Blutscrums und des HiOiner- 

 eiweisses." Pfliiger's Archiv, Vol. ix. pp. 514 552. 



5 Winogradoff, "Darstellung und Eigenschaften salzfreier Eiweisslcsungeu." 

 Pfliiger's Archiv, Vol. n. p. 605. 



