PRACTICAL DISIXFECTIOX AND STERILIZAT1' >\ 127 



observers, with varying results. The differing results can probably be 

 explained by difference in technique and in the kind of lime used. It 

 JN absolutely necessary to have a quick slaking lime or a great amount 

 of the gas will be lost by polymerization into paraformaldehyde and 

 acrose. Even with quick slaking lime, if it is not spread in a com- 

 paratively thin layer, polymerization takes place; therefore, in applying 

 the method a wide pan must be used. The addition of concentrated 

 sulphuric acid to the formaldehyde solution in the proportion of 10 

 per cent, immediately before using lessens the danger of polymeriza- 

 tion and makes the evolution of the gas much more rapid. The sul- 

 phuric acid must not be added to the formaldehyde solution until just 

 before using, for it causes rapid polymerization in the solution. It 

 must be remembered, also, that sulphuric acid is a dangerous agent, 

 and careless handling of it might result in serious burns. The technique 

 of the method is as follows: To ten ounces of 40 per cent, formaldehyde 

 solution slowly add one ounce of concentrated sulphuric acid; pour this 

 solution on to two pounds of quicklime that has previously been cracked 

 into small lumps and placed in a dairy pan not less than twelve inches 

 in diameter. The liberation of a large amount of gas in a short time 

 more than compensates for the loss by polymerization, and disinfection 

 is effected by a quick union of the gas and organisms to be destroyed. 

 Saturated solution of aluminum sulphate may be used instead of con- 

 centrated sulphuric acid, in the proportion of one part of aluminum 

 sulphate solution to three parts of 40 per cent, formaldehyde solution. 

 The mixture of aluminum sulphate and formaldehyde will stand for 

 considerable time without polymerization. Good results have been 

 obtained from pouring 40 per cent, solution of formaldehyde into com- 

 mercial permanganate of potassium in the proportion of six ounces of 

 permanganate for every pint of 40 per cent, solution of formaldehyde. 

 Rapid Generation of Formaldehyde Gas for Large Chambers by the Method 

 of Dr. R. J. Wilson. The generator is made of ordinary iron steam pipe 

 and can be manufactured in any pipe-cutting establishment in a very few^ 

 hours. It consists of an outer steam jacket of six-inch pipe, two feet 

 long, and capped at both ends. Through the upper cap there is a four- 

 inch opening, with a thread, through which projects an inner chamber 

 for formalin. This chamber consists of a four-inch pipe, twenty-two 

 inches long, capped at the upper end and welded or capped at the 

 lower end. The upper end of this pipe is so threaded as to permit of 

 its being screwed through the cap of the steam jacket before that cap 

 is screwed on. The cap of the formalin chamber is fitted on the 

 same thread that passes through the cap of the steam jacket. The 

 in-take for steam is near the top of the steam jacket, through a half- 

 inch pipe, and the steam is controlled by a globe valve. The outlet 

 for steam or drip is through a half-inch pipe from the bottom cap of 

 the chamber and is also controlled by a globe valve. The in-take for 

 formalin is through the upper cap of the formalin chamber through a 

 half-inch pipe controlled by a globe valve. The outlet for formaldehyde 

 is a half-inch pipe through the upper cap of the formalin chamber. 



