A manual of practical hygiene / by Edmund A. Parkes ; edited by F.S.B. Francois de Chaumont.

Date:
1878
Catalogue details

Licence: Public Domain Mark

Credit: A manual of practical hygiene / by Edmund A. Parkes ; edited by F.S.B. Francois de Chaumont. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

    226/820 (page 180)
    The suspended matters may be collected very simply by Pouchet's aeroscope. A small funnel is drawn into a small point, below which is a slip of glass moistened with glycerine. The end of the funnel and a slip of glass are inclosed in an air-tight chamber, from which a small glass tube passes out and is con- nected by india-rubber tubing with an aspirator. As the water runs out through the aspirator, air passes down the funnel and impinges on the gly- cerine, which arrests any solid particles. As it is, however, desirable to avoid glycerine, which may (in spite of previous careful examination) contain foreign particles, a still better plan is, to take a small bent tube, wash it thoroughly, dry it, and heat it to redness; when cool, it should be placed in a freezing mixture, an india-rubber tube be fixed on one end, and air slowly drawn through ; the water of the air condenses in the tube, and'many of the solid particles fall with it. A drop is then taken by a perfectly clean glass rod, previously heated to redness, placed on a clean lass and looked at with an immersion lens, as soon after collection as pos- SlblS. Or air may be drawn through pure distilled water, a drop of which is then examined. . Dr Watson (Staff-Surgeon), in his examination of the air at JN etley,* used fine glass threads soaked in pure glycerine, or dry, and crushed glass; after the air was drawn through, he washed the glass threads with pure water, and then examined the water. These glass threads form good traps for the larger particles.f An aspirator, to draw air through the tubes, is very easily made; a square tin vessel, with a tap below, and a small opening above to receive the mdia- rubber tube, is all that is necessary; fill this with water, and let it run down, and measure the total quantity (in a pint vessel) discharged without tilting the vessel. An imperial pint contains 34-659 cubic inches, and one fluid ounce 1-733 cubic inches. A cubic foot is very nearly 1000 fluid ouuces, and the ounce may be taken as 1-728 cubic inches.* The exact delivery of the aspirator is, therefore, easily determined j the air should be drawn slowly through the bent tube in the freezing mixture or through the aeroscope, so that no particles can escape. Chemical Examination. 2. Estimation of Carbonic Acid.—Fox our purpose the method proposed by Pettenkofer is the best. A glass vessel is taken capable of holding J gallon, or 4£ litres. The capacity is determined by filling it with water, and by measuring the contents by means of a litre or pint measure (1 oz. = 284 cubic centimeters). The vessel is thoroughly dried, and is then filled with the air to be examined, which is most readily done by pumping in the air with a bellows. Angus Smith recommends extracting the air from the bottle. When this is done 60 C.C. of clear lime or baryta water are put in, and the mouth is closed with an india-rubber cap.§ The vessel is agitated, so that the lime water may run over the sides, and then is left to stand for not led than six or eight hours if lime-water be used; if baryta-water be used the experiment may be completed in a much shorter time, less than one hour. I SfflJSfS t&SLm of bottles coiningpure disced water the. bestJinn, for the sediment is examined by the microscope, and the liquid part can he used for chemical examinations for organic matter. (F. dc C.) T£ nmnbers are exact at 39' Pahr., or the maximum density point of water t i ir. india-rubber cap not be available, a cork or a bung may be used, tied over *ith ],!th«£ 0! oil Wn ; in «mt caie the second alkalinity of the lime-water (if this be used)^should fi^determined Is soon after the six or eight hours as possible, certainly w.thm 24 hours.