8 
t 
therein and quite a variation in the percentage was noted. The highest 
was 52 per cent, which was in a sample sent by a manufacturer, but it 
soon decreased to 43 ; the lowest was 29 per cent. 
Bernard Smith (2) examined 29 samples and the lowest percentage 
he found was 32.45 per cent and the highest 39.11 per cent, the aver- 
age of the 29 samples being approximate!}" 37 per cent. My work was 
done with solutions varying from 37.2 per cent to 37.4 per cent and 
will be discussed in percentages of formalin, the name by which the 
watery solution is best known, of about 37. 2 per cent formic aldehyde. 
• To Passed Asst. Surg. M. J. Kosenau I am much indebted for sug- 
gesting this study and for suggestions as to the work. Also, to Dr. 
J. H. Kastle and Asst. Surg. Norman Roberts, who very kindly col- 
lected for me most of the data on methods of preparation and tests. 
PROPERTIES AND USES. 
Eormalin or solution of formaldeh^^de is an aqueous solution con- 
taining not less than 37 per cent, by weight, of absolute formaldeh}"de 
(U. S. P.). Formalin is a clear, colorless liquid with a sharp, pene- 
trating odor, caustic taste, and is very irritating to the mucous mem- 
branes. It mixes with alcohol and water in ail proportions. When 
subjected to low temperatures it becomes turbid, due to the formation 
of paraformaldeh3"de. It is not corrosive to the metals, except unpol- 
ished steel and iron. It combines readily with albumin, and its germi- 
cidal action is due to its combination with the cell body of the bacterium. 
It is used to some extent for tanning leather. Its use as a preserva- 
tive of cadavers in embalming fluids is wide. It enters into the com- 
position of Orth’s and Kaiserling’s solutions, and is f requentl}" used for 
fixing of specimens in microscopical work. It has been used illegally 
for the preservation of various food products, especially milk and 
cream. It is also used to some extent by farmers for the destruction 
of harmful fungi, such as smut on seed grain and scab on potatoes. 
The gas evolved by various methods from the solution is one of our 
most efficient gaseous disinfectants. 
According to Fischer 2 cubic centimeters of a toVo formalin solution 
per 100 grams of body weight given intraperitoneally will kill guinea 
pigs. In whatever way it is introduced into the body it is capable of 
producing lesions in the parenchymatous organs. 
DISCOVERY AND METHODS OF PREPARATION. 
Formic aldehyde was first obtained b}" Hoflinan (3) in 1867. He 
made it by passing the vapors of methyl alcohol, laden with air, over 
a heated platinum spiral. 
In 1875 J. Yolhard (4) obtained it in the following manner: A coil 
of platinum wire was heated in the flame of a wood spirit lamp. The 
