2(1 DENSITIES OF OXYCEN AND HYDROORN 



same ghvss. Tliis was then cemented with wax to the joint </, iii.ulf nf soft glass, 

 which was in turn fused to tlie rest of the ai>i>aiatus. 



It mav he said that not a single eoiineetion of rubher was used, in any of my 

 e.\|>eriments, in contact with the gas on wliich I was working. It is of course true 

 that witli I ubljer joints the leakage may be so small as to be estimated and allowed 

 for. Mut it was desirable to have no leakage at all, or, lather, to have no more than 

 that which is inevitable between gla.ss ami mercury; and the maniimlation which 

 dispenses with rubber joints is by no means troublesome. 



u^ 



I 



Fig. 7. — .Apparatus for iireparing oxygen ; f /g shows in plan the tubes seen in elevation to the right of c. 



At c is a gauge and overflow tui)e dip[)ing in raercin) . i'lie o.xygeii coming 

 from d, in .some experiments, pa.ssed through a tube containing linely divided silver 

 heated to redness, in order to absorl) chlorine. When this was used it was con- 

 nected to the tube a by fusion, and the joint d was at the end of the tube 

 containing silver. The L'as ne.xt passed through a tube 1 metiv long, and 2.5 

 centimetres in ilianieter, which was fillctl with glass beads moistenetl with a strong 

 solution of potassium hydrt).\ide ; then thi'ough a similar tube with sulphuric acid. 

 At this point was placed a stojjcock, w'hose office was to keep the pressure of the 

 oxygen filling the part of the apparatus so far desciibed at about the pressuie of the 

 atmosphere, so as to allow sufficient time for the action of the reagents. The tubes 

 lay horizontally, so that the reagents might be advantageou.sly distributed. After 

 the sto[)cock, the gas passed through a tube of the same dimensions, filled with 

 phosphorus pentoxide between layers of glass wool. From this, it wj»s led to the 

 apparatus which was to be filled with it. 



In preparing oxygen, the a})paratus was exhausted, and the degree of ex- 

 haustion measured ; it was commonly the thirty-thousandth or fifty-thousandth of an 

 atmosphere. Then the stopcock h was shut, and the chlorate was heated till it was 

 thought safe to assume that any organic matter pieseiit had been oxidized. The 

 chlorate was then cooled, the stopcock /t was opened, and the apparatus was again 



