Practical bacteriology for chemical students / by David Ellis.

  • David Ellis
Date:
1923
Catalogue details

Licence: In copyright

Credit: Practical bacteriology for chemical students / by David Ellis. Source: Wellcome Collection.

    16/152 (page 4)
    tu-re. The principle under which all efficient incubators work is the same throughout the various types viz. that an increase in the temperature of the vessel produces some effect which cuts off the source of the heat. Not altogether, however, for a bye-pass is present which keeps up a small flame when the Fig. 4. — Diagrammatic representation of the parts of a gas-valve regulator. The boiling of the liquid in the capsule raises the lever B and depresses the lever A. This closes the valve through which the gas is issuing. The burner is now fed only by the bye-pass. When as a result the temperature falls, the lever B is depressed and the lever A is raised with the result that the gas flews through the valve once more. It is clear that the temperature of the incubator will be approximately the temperature of boiling of the fluid in the capsule. A slight variation can be obtained by shifting the sliding-weight along the lever making this more or less difficult to be raised. main source of heat is cut off. The vessel cools as a result of the cutting off of the main supply of heat. As this supply has been cut off by the expansion of some substance, the cooling of this substance naturally brings the main supply once more into operation. In this way the temperature cannot go up very far for the main supply is cut off when the temperature reaches a certain point, and cannot go down very far for a lowering of temperature brings it once more into operation. By far the best of these gas-valves is a type in which