BAIRD &TATLOCK (LONDON) LTD. 



The various parts of the apparatus are suitably mounted on a strong wooden stand (oak or teak), with four vertical steel 

 rods supporting the shelf upon which the mercury trough G rests, the same rods also carrying another shelf for reagent bottles. 

 Proper provision is made for the raising or lowering (to the ground level if required) of the mercury reservoir D by means of a 

 wooden carrier with suitable pulley and ratchet wheel. The whole apparatus stands in a wooden tray 2 ft. 4 in. by i ft. 6 in. 

 with i in. raised sides. 



The salient features of the working of the apparatus are as follows : 



1. The principle of measurement employed is that first introduced into gas analysis by Regnault, and subsequently adopted 

 py Sir Edward l'"rankland, viz., the measurement of the pressure of gas (in millimetres of mercury) at constant volume. For 

 :his purpose the gas is brought to a certain " constant volume " mark in the measuring tube A (by suitable manipulation of the 

 nercury reservoir D and the tap c) and its pressure read off on the pressure tube B. There are a series of such " constant volume " 

 marks on A, each coinciding with a 100 millimetres mark on the pressure tube B (i.e., with o, 100, 200, etc., millimetres), so that 

 lie actual pressure of the gas is given by subtracting from the " pressure reading " the numbers o, too, or 200, etc., according 

 :o the particular constant volume mark selected for the analysis. The tubes A and B are made in one piece, which is surrounded 

 >y a water jacket, and their inner surfaces are kept moist with very dilute sulphuric acid (i in 20) as a precaution against the 

 iccidental fouling of the measuring tube with alkalies, and it is obvious that the wetting of A and B with the same liquid eliminates 

 the influence of water vapour upon the gas measurements, the various pressures representing those of the dry gas under examina- 

 tion. The tap closing the upper end of the pressure tube is connected with it by means of stout rubber pressure tubing, a device 

 Iwhich gives a perfectly tight joint with sufficient elasticity to prevent fracture in case the mercury in B is inadvertently allowed 

 to run up the tube with unusual velocity. The tap in question also allows of the vacuum being easily made in B whenever neces- 

 sary. The advantages of this mode of measurement over the more usual method of detenmining the volume under atmospheric 



ipressure are twofold, viz., (i) it allows of the use of smaller volumes of gas for an analysis, thus from 5 to 10 cubic centimetres 

 of gas can be made to have a pressure of 100 millimetres, according to the particular volume mark selected, and this pressure 

 ban easily be read off to within 0.2 millimetre, without employing a telescope, and (2) the measurements are, of course, independent 

 jf the barometric pressure, and at the same time are unaffected by tension of aqueous vapour. 



2. The length of the pressure tube B (about 700 millimetres) amply provides for the proper dilution of the " explosive mixture " 

 in an explosion analysis, even in the case of a rich gas such as coal gas. 



3. The arrangements for the various " absorptions " are of the simplest. Instead of using a number of large absorption 

 ivessels each containing a particular reagent, which is used unchanged many times over in successive analyses, all the absorptions 

 jire carried out over mercury in the one absorption vessel r, in each case with a comparatively small volume of the particular 



nt, which is always used fresh and is at once discarded after use. 



To facilitate the introduction of the various reagents, and the rinsing out of the absorption vessel with water or dilute 

 sulphuric acid in situ between each successive reagent, the wide (open) end of the vessel is immersed under the mercury in the 

 'trough G, whilst the top terminates in a capillary three-way tap K. One of the parallel branches of this tap communicates through 

 i stout rubber joint with the measuring vessel A, and the other with a water pump, a large bottle being inserted between the pump 

 md the absorption vessel to serve as a trap for either the mercury or the reagent which is being discarded after use. The insertion 

 )f a tap between the pump and the bottle obviates the necessity of the continuous exhaustion of the latter, a single exhaustion 

 it the outset of an analysis being all that is required. 



From 2 to 5 cubic centimetres of the particular reagent to be used is introduced into the absorption vessel (previously filled 

 vith mercury), by means of a suitable pipette, from below the surface of the mercury in the trough. Any minute bubble of air 

 accidentally introduced with the reagent can be got rid of by cautiously opening the branch of the tap K leading to the above- 

 mentioned exhausted bottle ; the same device allows of the complete withdrawal of the reagent after use, without taking down 

 ' he absorption vessel, and also of the rinsing out of the latter in situ with water, or dilute sulphuric acid, before the next reagent 

 s used . 



4. In point of rapidity of action, combined with accuracy, the apparatus will compare favourably with any other type. An 

 malysis of producer gas can be easily carried out in forty-five minutes, and one of coal gas in about an hour. 



5. There are no complicated parts about the apparatus to occasion trouble, and the several parts can be readily detached 

 or cleaning purposes. 



6. The apparatus is well adapted for the analysis of almost every kind of combustible gaseous mixture, ordinarily met with 

 n technical practice, including producer gas, water gas, natural gas, oil gas, coal and coke-oven gas, septic-tank gas, blast-furnace 

 ;ases, etc. 



N.B. Each apparatus ordered will be personally inspected and approved either by Professor 

 Bone or Mr. Wheeler before being despatched to the purchaser. Any further information as to its 

 vorking will be supplied on application by letter to Professor Bone, Imperial College of Science 

 nd Technology, South Kensington. 



For further description of the apparatus see " Journal Soc. Chem. Ind.," 15th January, 1908. 



ICHEMICAL AND SCIENTIFIC APPARATUS AND PURE CHEMICALS. 



869 



