154 
Proceedings of the Royal Society of Edinburgh. [Sess. 
caused greater retardation than when kept at room temperature. These 
facts seem to point to the inorganic constituents of the serum as the active 
factors, and suggested that the reaction might be similar to that of nitrous 
acid on many organic compounds. 
N 
Fig. 4. — Influence of serum on the reaction between sodium nitrite and 0’5 per 
400 
cent, solution of washed blood corpuscles. The amount of serum is indicated 
against the curves. The unmarked curve shows the course of the reaction 
Avithout serum. 
Ordinates , extinction coefficients ; Abscissae, time in minutes. 
Effect of Sodium Hydroxide. — Alkali, when added to the solution of 
blood or to the solution of nitrite, also caused marked delay in the appear- 
ance of the reaction. The effect of different concentrations of sodium 
hydroxide on the reaction is seen in figs. 5 and 7. Fig. 5 shows the effect 
of one-thousandth, two-thousandth, and four- thousandth normal sodium 
hydroxide on the reaction between two-hundredth normal sodium nitrite 
and a 2 per cent, solution of blood. Five-hundredth normal sodium 
hydroxide tested under the same conditions prevented any change for two 
and a half hours, when the experiment was discontinued. The delay in 
the reaction is dependent, however, not only on the concentration of sodium 
hydroxide, but also on that of the sodium nitrite. This is seen in fig. 6, 
which illustrates the effect of twentieth normal and of two-hundredth 
normal sodium nitrite on a solution of 05 per cent, blood corpuscles in 
thousandth normal sodium hydroxide. With the same strength of blood 
corpuscles in distilled water the reaction with four-hundredth normal 
sodium nitrite was completed in little more than a minute. The slight 
