14 
11. 43 c. c. ^ AgNOg sol. = Quantity combined with KCN. 
2. 88 c. c. ^ AgN0 3 sol. =the formaldehyde absorbed. 
n 
10 
lc. c. A AgNOg sol. represents 0.003 gm. formaldehyde. 
Then, 0.003 X 2.88 = 0.00864 gm. formaldehyde in 10 liters of air. 
air (28.315 liters) contained 0.0245 gm. formaldehyde. 
Therefore, 1 cu. ft. 
The titres of the sulphocyanate and cyanide solutions were as 
follows : 
10 c. c. KCNS solution = 10. 21 c. c. ^AgN0 3 solution. 
10 c. c. KCN solution = 9. 54 c. c. T AgNO s solution. 
(b) Absorption in mater . — Tubes 1, 2, 3, 4, 5 contained a column of 
distilled water from 1 to 1.5 inches high. After making connections, 
air was drawn through them from the room, as already described. 
Volume of air drawm from room = 10 liters. 
Time required to draw air = l hr. 13 min. 
Ten c. c. KCN solution were placed in a 300 c. c. beaker and the con- 
tents of the five tubes and their connections carefully rinsed into it. 
This solution was then transferred to a 250 c. c. flask containing 10.1 
c. c. — AgNOg solution plus 8 to 10 drops of nitric acid. The flask 
was filled to the mark with water and thoroughly shaken. 
The subsequent procedure is exactly like that given under a above, 
except that not the corrected titre, but the original titre of the cyanide 
solution is used in the calculation, since the cyanide solution is not 
subjected to the action of air bubbling through it. 
Th 
Volume of — AgNOg solution corresponding to formaldehyde ab- 
sorbed = 3.03 c. c. 3.03 c. c. X 0.003 = 0.00909 gm. formaldehyde in 
10 liters of air. One cu. ft. (28.315 liters) air contained 0.0257 gm. 
formaldehyde. 
The quantity of formalin used to charge the room in nearly all the 
experiments, tabulated further on, was 600 c. c. of 35.66 per cent by 
volume — i. e., 100 c. c. of the formalin contained 35.66 gm. of absolute 
formalin. The strength was determined by the Blank and Finken- 
beiner method of titration with hydrogen dioxide and caustic-soda 
solutions.® In all the experiments the formalin was taken from the 
same supply. 
In the two experiments just described 600 c. c. of formalin were 
used to charge the room. The results may be expressed in percentage, 
a For description see original article in Berichte, 1898, p. 2979, or the U. S. Pharmaco- 
poeia, Eighth Decennial Revision. 
