Adeney — An Apparatus for Gas Analysis, 8fc. 543 



burette is held in its place by the brass plate b, one end of which is 

 bent at right angles and screwed to the stand, and the other end is 

 bent and cut to fit and clamp the upper part of the stopcock as 

 indicated in the drawing. By this means the burette is clamped 

 firmly, but sufficient play is afforded for contraction or expansion 

 of the glass by alteration of temperature. 



The supply of mercury to the burette and pressure tube is 

 regulated by means of a reservoir which can be raised or lowered 

 by a pulley and small windlass c, fixed to the back of the stand. 

 The flexible tube from the reservoir passes through a hole in the 

 back of the stand at d, and is attached to the pressure tube by 

 means of the small side tube e. The necessity of attaching the 

 connecting tube from the reservoir to the pressure tube, and not 

 directly to the burette, will be explained later on. 



The height of mercury in the pressure tube is read off by means 

 of a millimetre scale etched on the unsilvered surface of the narrow 

 slip of looking-glass//", which is fixed close to the back of the pres- 

 sure tube and inclined to the vertical plane, as shown in the 

 drawing, so as to reflect the image of the tube from the portion of 

 the glass bearing the scale. To read the height of the mercury in 

 the tube the eye is held a little to the right of the scale, and moved 

 about a little until the scale lines in the immediate vicinity of the 

 reflected image of the mercury meniscus coincide with their images 

 reflected from the silvered surface of the glass. When the eye is 

 in this position the height of the mercury can be accurately read to 

 0-5 mm. and with aid of a lens to about 0*25 mm. 



The burette and pressure tube are each provided with a 

 Friedrich's patent glass stopcock of the pattern shown in the draw- 

 ing. Two branch tubes, g, h, spring from the stopcock of the 

 burette ; the former is a capillary tube and serves to connect the 

 burette with the laboratory vessel and other purposes, while the 

 latter is of wider bore (2 to 3 mms.) and is intended to connect the 

 vessel containing the substance to be examined with the burette. 

 The two tubes are firmly held against the wooden block k, which 

 is grooved to receive them, by a brass plate lined with cork and 

 screwed to the said block. It is necessary to support the two tubes 

 thus to obviate the danger of their being broken off from their 

 junction with the stopcock by a sudden blow or undue pressure. 

 When firmly held in the manner described, the tubes will bear 



