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This paper describes a tip made of Pyrex glass to be used in a gas-absorption pipette to divide the stream of gas into small bubbles in order to obtain a large surface of contact with liquid reagents. The tip is made by sealing a number of fine copper wires, radiating from a center in a definite pattern, between a cone form ed on the end of a glass tube and a circular glass disk. After the glass parts are sealed together and ground to expose the ends of the wires, the wires are dissolved in warm nitric acid. Drawings which illustrate the method of making the tips are included. The tips are very sturdy and at moderate pressures furnish small bubbles of uniform size and distribution. Tms paper describes a tip used for dividing a gas stream into bubbles for the washing of gases or for their absorption in liquid reagents. The tip was developed primarily for the absorption of oxygen in an alkaline solution of potassium pyrogallate in an Orsat apparatus. It is, of course, adaptable to other reagents and to other forms of apparatus. Each unit of the Orsat apparatus for wmch the tip was designed was made of Pyrex glass a,nd sealed directly together to avoid rubber connections. 1 The extent to which absorption is accelerated by dividing the gas stream passing through the reagent into small bubbles wmch offer a large surface of contact has been discussed in connection with two gas-absorption pipettes previously described. The gas entering the inlet tube of these pipettes is divided into small bubbles by passage through either a platinum disk drilled with several hundred orifices, 0.06 mm in diameter,2 or through a porous Jena glass thimble. 3 Other types of porous or perforated disks have also been used to some extent, particularly in wash bottles. The absorption pipette described in tms paper is shown in figure 1. The dimensions of all drawings are given in millimeters. The front and top views of the assembled distributor tip are shown in figure 2, A and B, respectively. At the left, in figure 2, are shown crosssectional views of the parts 0, D, and E, from wmch the tip is made and the top view of the copper spider, F, which is sealed between 0 and E at D. A thin copper disk, G, may be substituted for F, if desired. The spider, F, constructed of small copper wires, as is described later, or the thin copper disk, G, serve as temporary spacers which are later dissolved in mtric acid to leave channels of like shape in the glass. After E is sealed to 0 the outer ends of the wires forming 1 For a discussion of errors caused by such connections, see, J . R. Branham, Errors in gas analysis arising from 108s oJ gas by .olution in rubber connections and 8topcock lubricant, BS J . Research 12, 353 (1934) RP661. 'Martin Shepherd, A gas anaWsis pipetteJor difficuU absorption8. BS J . Research 4, 747 (1930) RP177. 'Martin Shepherd, Fish·Schurman Catalogue, p. 18.

Bubbler tip of pyrex glass for difficult absorptions