. Public health laboratory work, including methods employed in bacteriological research, with special reference to the examination of air, water and food contributed . t least of the chemical reagents, , those whichare in most common use. By the side of the benchthere should be a tap (furnishing a good supply of purewater), with, if possible, a small water sink beneath must be gas in the room, but not necessarily nearthe bench, for it can be readily conducted thereto bytubing. A Bunsen gas burner is required, and it is B 2 LABORATORY WORK. very desirable to have two of these, so t
. Public health laboratory work, including methods employed in bacteriological research, with special reference to the examination of air, water and food contributed . t least of the chemical reagents, , those whichare in most common use. By the side of the benchthere should be a tap (furnishing a good supply of purewater), with, if possible, a small water sink beneath must be gas in the room, but not necessarily nearthe bench, for it can be readily conducted thereto bytubing. A Bunsen gas burner is required, and it is B 2 LABORATORY WORK. very desirable to have two of these, so that both can beutihsed at the same time. The Bunsen burner (fig. i)consists of a larger external tube surrounding a smallergas-delivering one at its base, the former being per-forated for the admittance of air—so that at the topthe gas escapes well mixed with air, and hence oxida-tion (and therefore heat) in the flame is increased. The apparatus required:— I. A pair of balances with weights. Oertlings No. 3(Townson and Mercers Catalogue) will be found to beextremely suitable to all purposes. As shown in theaccompanying diagram, they consist of a twelve inch. Fig. I.—The Bunsen burner. beam which supports two pans, the ends of the beambeing constructed with straight knife edges upon whichthe pans are suspended by agate planes. The case isfitted with a sliding window in front, which can beclosed and still admit of the scales being made toregister by means of a screw which projects externally. The operation of weighing consists of first lifting thebeam off its support by means of the screw, and thennoting by the long indicator which hangs down in frontof the central vertical support of the balances—andwhich must come to rest in an absolutely central andvertical position—whether the two pans exactly coun- HYGIENIC ANALYSIS OF WATER. 3 terbalance each other ; if not the balance must be ad-justed by means of a small mechanism situated on thetop of the centre of the cross-be
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Keywords: ., bookcentury1800, bookdecade1890, bookpublisherphiladelphiablakis
