Dec. IS. 1914 Coloring Matter of Salted Meats 2 1 3 



partial reduction of the saltpeter to nitrites by heating the dry salt in a 

 kettle before it is to be used. It is stated that this partially reduced 

 saltpeter is much more efficient in the production of color in the manu- 

 facture of sausage than is the untreated saltpeter. 



Humphrey Davy in 1812 (cited by Hermann, 1865) and Hoppe-Seyler 

 (1864) noted the action of nitric oxid upon hemoglobin, but it appears 

 that Hermann (1865) was the first to furnish us with much information 

 as to the properties of this derivative of hemoglobin. He prepared 

 NO-hemoglobin by first passing hydrogen through dog's blood until 

 spectroscopic examination showed that all of the o.xyhemoglobin had 

 been reduced to hemoglobin, then saturating the blood with pure nitric 

 oxid prepared from copper and nitric acid, and finally again passing 

 hydrogen through the blood to remove all traces of free nitric oxid. It 

 was observed that the spectrum of hemoglobin had changed to one 

 showing two bands in practically the same position as those of oxyhemo- 

 globin. The blood saturated with nitric oxid was found to be darker in 

 color than either arterial blood or that saturated with carbon monoxid, 

 and on exposure to air or on treatment with ammonium sulphid it 

 proved to be as stable as carbon-monoxid hemoglobin. 



NO-hemoglobin is mentioned but briefly in most of the recent texts on 

 physiological or organic chemistry as being a hemoglobin derivative of 

 but little practical importance. Abderhalden (191 1) and Cohnheim 

 (191 1), however, describe this compound quite fully. 



EXPERIMENTS WITH NO-HEMOGLOBIN 



The following studies on NO-hemoglobin were conducted by the 

 writer. 



Formation. — Nitric oxid was prepared by treating copper foil with 

 concentrated nitric acid, and the production of the gas was carried on 

 long enough to free the apparatus from higher oxids of nitrogen before 

 conducting gas into the solution of hemoglobin. A simple apparatus 

 was arranged so that the sample of blood or of hemoglobin to be treated 

 was first saturated with pure hydrogen, then with nitric oxid, and 

 finally again with hydrogen to remove all free nitric oxid. Great care 

 was exercised to exclude air from the apparatus, since the presence of 

 even a small amount of free oxygen results in the oxidation of nitric 

 oxid to nitrogen peroxid, with the consequent production of nitrous and 

 nitric acids, which act upon hemoglobin to form methemoglobin. 



NO-hemoglobin was prepared, in the manner described above, both 

 from defibrinated blood and from a solution of oxyhemoglobin prepared 

 by Hoppe-Seyler's method. It was found, as a rule, that if a solution 

 of oxyhemoglobin or of defibrinated blood was treated with nitric oxid, 

 with all precautions to exclude free oxygen, the NO-hemoglobin usually 

 contained a small amount of methemoglobin. This fact has been 

 noticed by other investigators and is due to the union of the loosely 



