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.

    9/20 (page 3)
    A more sensitive test has therefore been developed from the bleaching powder test. If, after the addition of the bleaching powder, the solution is made alkaline with ammonia and a dilute aqueous solution of phenol added, a permanent deep blue colour is produced even with minute quantities of aniline. This test has been adopted as the standard test for aniline vapour in industry. It has been made quantitative by comparing the colours obtained at known concentrations with a series of standard colours prepared from a dye.* In this way a table has been drawn up showing the depth of colour obtained with up to 10 strokes of the standard hand pump over a range of concentrations from 1 part in 5,000 to 1 part in 100,000. The table is included in the detailed instructions for performing the test given below. Instructions for Carrying out the Test for Aniline Vapour The test shall be carried out in accordance with the following instructions :— General : Although the test is simple and accurate, it shall only be carried out by a responsible person appointed by the occupier; this is definitely required by Regulation 7 of the Chemical Works Regula- tions, 1922, in the case of entry into vessels. All necessary steps shall be taken for the protection of the person carrying out the test. In determining the concentration of aniline vapour in a workroom samples shall be taken at a point closely adjacent to the workers, aS an average sample for the whole workroom may give misleading figures of the concentrations actually inhaled. Regular periodical tests will enable a rising concentration to be detected and ensure that an undesirable level is never attained. In determining the concentration of aniline vapour in the atmosphere inside a tank prior to the entry of a workman, it may be insufficient to do only one test. When there is any chance of the concentration inside the tank rising, sampling shall be carried out at intervals throughout the period of work. Apparatus The atmosphere being tested shall be sampled by means of a hand exhausting pump with a barrel of approximately 1-25 in. bore and a capacity of 126 ml. The pump shall be fitted with a nozzle opening for attaching rubber tubing ; it may also be provided, if desired, with a device for counting the number of strokes made. The sample shall be drawn through the reagent contained in a bubbler consisting of a side-arm test tube of approximately 0-75 in. internal diameter and about 6 in. in length, fitted with a rubber bung through which passes a delivery tube (approximately 0-125 in. bore)