Volume 1

Methods of practical hygiene / translated by W. Crookes.

  • Karl Bernhard Lehmann
Date:
1893
Catalogue details

Licence: Public Domain Mark

Credit: Methods of practical hygiene / translated by W. Crookes. Source: Wellcome Collection.

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    are closed by turning a ring, the supply of air ceases, the Tame becomes yellow, luminous, smoky, and produces little heat. Eor chemical operations a non-luminous flame is exclusively used, hence cheap burners are often made without the closing-ring. The greatest heat is found at the pale violet point of the flame and at its margin. The capsule (especially platinum vessels) is not to be intro- duced beyond the upper third part, a. The colourless zone b, which surrounds the greenish-blue, cool, internal core of the flame, exerts a reductive action in consequence of the hydrogen which it contains; the point and the outer sur- face are the seat of energetic processes of oxidation. If we wish to work with a small heating-flame, this is best effected by decreasing the current of gas, and at the same time reducing the supply of air by partially pushing forward the closing ring. If this precaution is neglected the flame is apt to strike back, i.e., the gas burns no longer at Iig. 3. Bunsen bmnei. ppg aperture of the burner but at the fine slit n. There escape then, along with carbon-monoxide, gases of an unpleasant odour, especially acetylene ; the burner quickly becomes hot, and is coated internally with soot, whilst the flexible gas-pipe may take fire. As soon as a burner strikes back the flame must be put out and be lighted again.. The precaution must first be taken of letting a strong current of gas rush through, kindling it at the burner, and then regulating the flame. A small piece of fine wire gauze fixed over the mouth of the burner is a good precaution against striking back. In default of gas it is possible to work satisfactorily with
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