526

Siphons used hy Chemists.

[Book V.

in Operation by tbe lungs. Moreover cocks and valves of metal are actedon by acids, and in some cases would affect or destroy the properties ofthe fluids themselves.

No. 259.

No. 260.

No. 261.

No. 258

No. 258 shows bow bot or corrosive liquids may be drawn off from awide mouthed bottle or jar. The short leg of a siphon is inserted throughthe cork ; and also a small tube, through which the operator blows, andby the pressure of his breath forces the liquid through the siphon.

No. 259 represents a siphon sometimes employed by chemists. Whenused, the short leg is first placed in the fluid to be decanted, the flame ofa lamp or candle is then applied to the underside of the bulb ; the heatrarefies the air, and consequently drives out the greater part of it throughthe discharging orifice. The finger is applied to this orifice, and as the bulbbecomes cool the atmosphere drives up the liquid into the void and putsthe instrument in Operation.

No. 260 is a siphon by M. Collardeau. It is charged by pouring aquantity of the fluid to be decanted into the funnel; the bent pipe attachedto which terminates near the top of the discharging leg. The fluid indescending through this leg bears down the air within it, on the principleof the trombe, and the atmosphere drives up the liquid in the reservoirthrough the short leg. In experiments with this instrument we invariablyfound the contents of the eharging tube drawn into the siphon wheneverthe orifice of the discharging leg was not made smaller than the bore ofthe receiving one. By not attending to this, such siphons will only act aslong as water is poured into the funnel.

No. 261. A glass siphon for decanting acids, &c. It is ; charged bysucking, and to guard against tbe contents entering the mouth, a bulb isblown on the sucking tube. The accumulation of a liquid in this bulbbeing visible, the operator can always withdraw his üps in time to pre-vent his tasting it.

No. 262 is designed to retain its contents when not in use, so that onplunging the short leg deep into a liquid the instrument will operate. Thiseffect however will not follow if the end of the discharging leg descendbelow the flexure near it, and if its orifice be not contracted nearly to thatof a capillary tube.

No. 263 is a siphon by which liquids may be drawn at intervals, viz.by raising and lowering the end of the discharging leg according to thesurface of the liquid in the cistern.

Our own labors have developed some novel modifications of the siphon.No. 264 is charged by an apparatus designed as a substitute for thesyringe. (See No. 255.) The sucking tube of an ordinary siphon is madeto pass through the centre of a much larger pipe. This is closed at thebottom, open at top, and its length equal to that of the short leg. A tnove-able tube open at bottom and closed above is fitted to slide in the last, andis of such a bore that the space between its sides and the exhausting tube