Aniline vapour / Department of Scientific and Industrial Research.

Date:
1939
Catalogue details

Licence: Public Domain Mark

Credit: Aniline vapour / Department of Scientific and Industrial Research. Source: Wellcome Collection.

    10/20 (page 4)
    reaching nearly to the bottom of the test tube, and terminating in a fine jet.* It is convenient previously to calibrate the test tubes to avoid measuring out the reagent each time a test is made. | The bubbler shall be mounted on the barrel of the pump in such a way that the reagent is easily seen, and the tube readily removable for comparison with the standard and replacement by a fresh tube. In order to prevent the reagent being accidentally drawn into the pump by too rapid pumping, a trap shall be inserted between the pump and the bubbler. ° A convenient arrangement} of the apparatus is shown in the diagram on page 5. The bubbler is fitted into a_ spring clip attached to a thin board fixed to the barrel of the pump; it can thus be readily withdrawn when required. The face of the board should be painted white or covered with a sheet of thin white porcelain or similar material. The trap employed consists of a small wide-necked bottle, carrying a rubber bung through one hole in which passes the nozzle of the pump. Through a second hole passes a glass tube (approximately 0-25 in. bore), terminating immediately below the bung, and connected by rubber tubing to one arm of a T-piece fastened to the board on the pump. The remaining arms of the T-piece are similarly connected to the side-arm of the bubbler and to one branch of a three-way tap, which is also fastened to the board. The remaining branches of the tap are connected as shown to the delivery tube of the bubbler and to the sampling tube. By suitable manipulation of the tap the bubbler can thus be by- passed, and air pumped directly from the sampling tube. This arrangement is convenient when tests are being carried out at a distance and it is necessary first to clear the pure air from the sampling tube. (See page 9.) The whole apparatus may be mounted in a wooden case by means of two spring clips into which the pump fits, the top face of the case being slotted so that the handle of the pump remains outside the case. The pump can thus be operated without removing the apparatus from the case; if necessary, however, the whole apparatus is readily * A convenient method of obtaining a jet of the correct size is to draw out the end of the delivery tube in a flame, and then to insert a wire of approxi- mately the required diameter (18-25 S.W.G. is suitable) until it is stopped. The jet is then cut at this point. ; his arrangement is intended merely to suggest a convenient way of assembling simple apparatus which would be likely to be available in any laboratory. Modifications in non-essentials may, of course, be made to suit individual circumstances or preference, e.g. by altering the lay-out, using all-glass bubblers or using permanent connexions. Some users may also prefer to purchase complete sets of apparatus offered by laboratory outfitters, which may differ in lay-out from the arrangement suggested. Such alter- native arrangements are quite permissible so long as they preserve the essential features of the apparatus described above, and may present practical advantages in manipulation.