The value of formic aldehyde gas in disinfecting is now generally recognized, but there have been many difficulties attending its efficient application. The volume used must be amply large and liberated with sufficient rapidity to overcome all the disadvantages. Dry heated gas is of highest value because it is most penetrating and, having a specific gravity equal to that of atmospheric air, mixes freely with air, thus producing its effects wherever air can penetrate.
In an effort to secure the best effects the following simple apparatus (shown in the illustration) has been devised. It consists of a Swiss heating lamp beneath a reservoir for commercial formaldehyde. Between these is a copper coil opening into the receiver and ending in a short gum hose, at the distal end of which is a thin feeding-tube. The opening from the reservoir into the tube is protected by a valve. When the tube is