Constant Water Baths.

[American Chemical Journal.]

The following simple form of constant water bath, which wastes no water, I have found to be very convenient:

A tube of glass or metal, not less than  1/4 of an inch internal diameter, the ends of which are cut off obliquely, is bent as shown in the cut. It should make an angle of about 30 deg., or a little greater, with the horizontal. The angle may be diminished if the bore of the tube is increased. One end is inserted in the water bath, the other in an inverted bottle. The height of the water in the bath is regulated by the depth of immersion of the tube in it. The boiling is not interrupted by the feeding, which takes place slowly and regularly. It is necessary that the ends of the tubes should be cut off obliquely. The same form of tube answers equally well for keeping a constant level in a filter or drying chamber.

A brass tube is much better than a glass one, as it does not crack at the water level after using for a time. Brass tubes can easily be bent by ramming full of sand, stopping the ends, and bending them over a curved surface. A large number of baths can be run by this apparatus by connecting them with a bath fed by it.—Charles T. Pomeroy.

Note.—We have used for a number of years in this laboratory a form of constant water bath which was contrived by Mr. Edward Bogardus, formerly chemist to the New Jersey State Geo­logical Survey. As I have not seen it described in print, and as it is cheap, simple, efficient, and ingenious, I will draw attention to it here.

The following cut represents the apparatus:

It consists of two tomato cans connected by a tin tube. Into one of the cans a bottle of water is inverted. We generally use a five-pound acid bottle. The other can makes the bath. This bath can be left running over night without fear. A large number of baths can be run by this contrivance by simply connecting them, by means of rubber tubes, with a reservoir replenished by an inverted bottle. Old fruit cans make excellent baths. A series of holes can be punched round the lower edge of a fruit can, thus affording a distributing reservoir. Corks holding short pieces of glass tube are inserted into the holes. By means of these the reservoir can be connected by rubber tubes with a number of baths at quite a distance. The baths are made by punching a hole near the lower edge of a fruit can and inserting a cork and short piece of glass tube. When the extra vents of the reservoir are not used, they can be closed by a short rubber coupling and a pinch cock.—Peter T. Austen, Chemical Laboratory of Rutgers College (New Jersey State Scientific School).