500 CHEMISTRY OF THE PROTEIDS CHAP. 



blood solution, the exact proportion depending on the quality of the 

 daylight at the time. The diluted carmine solution should be prepared 

 fresh when required, as its colour distinctly loses its strength when 

 kept for a few days. 



From the results of the titration with carmine solution the per- 

 centage saturation of the haemoglobin with carbonic oxide may be 

 easily calculated in the manner illustrated by the following example : 

 To 5 cc. of blood solution 6*2 cc. of standard carmine require to be 

 added to produce the saturation tint. To 5 cc. of blood solution 2*2 

 cc. of carmine require to be added to produce the tint of blood solu- 

 tion shaken with the air under examination. In the former case the 

 carmine was in the proportion of 6 '2 to 11*2 ; in the latter case in the 

 proportion of 2*2 to 7 '2. The percentage saturation of the haemo- 

 globin in the blood shaken with the air was thus : 



With 0*07 per cent CO in air, haemoglobin becomes half saturated with 

 CO. According to this result, the avidity of CO for haemoglobin is 

 300 times greater than that of 2 . Haldane, in some as yet unpub- 

 lished investigations, has found that with more prolonged shaking 

 blood or blood solution becomes half saturated with only 0*055 

 per cent of CO, which shows that the affinity of CO for haemoglobin 

 under perfectly normal conditions is about 380 times greater than 

 that of O 2 . The dissociation-curve, according to Haldane's present 

 views, is given on the opposite page. 



Carboxyhaemoglobin differs from oxyhaemoglobin also as regards 

 the ease with which it is converted into methaemoglobin. It is not at 

 all acted upon by hydroquinone and pyrocatechin, according to Weyl 

 and Anrep, 1 while oxyhaemoglobin is rapidly converted by these 

 reagents into methaemoglobin ; iodine-potassium iodide takes four 

 days and potassium permanganate twenty-four hours to form met- 

 haemoglobin. With a number of precipitating reagents, such as caustic 

 soda, caustic soda and calcium chloride, tannic acid or ferrocyanic acid, 

 CO-haemoglobin preserves its beautiful colour for a long time, while 

 ordinary haemoglobin is rapidly changed into a dirty brown or green 

 colour. (Hoppe-Seyler, Salkowski, 2 and Wahl. 3 ) The same is also 

 the case with sulphuretted hydrogen, which, according to Salkowski, 4 

 rapidly decomposes oxyhsemoglobin, while Carboxyhaemoglobin and 



1 T. Weyl and B. v. Anrep, Arch.f. (Anat. u.) Physiol. 1880, p. 227. 



2 E. Salkowski, Zdtschr. /. physioL Chemie, 12. 227 (1887). 



3 F. Wahl, Pfliiger's Arch. /. d. ges. Physiol. 78. 262 (1900). 



4 E. Salkowski, Zeitschr.f. physioL Chem. 7. 114 (1882) ; 27. 319 (1889). 



