( 87 ) 



tightly fixed completes the waterjacket. One of the glass side-walls of the 

 box M enables us in Ihe case of a leak in the apparatus, to find out where 

 the gas escapes. As in the water-bath alone there are twelve connections 

 with overpipes and nuts, this measure is not superfluous. 



During my observations at 9 to 10° the temperature in the room 

 exceeded that of the water-bath. In this case the water flows into the 

 apparatus through E and can leave it through the pipe F; we may then 

 expect the temperature of the water when flowing through to rise a 

 little, but by no means to fall. Thus we prevent the liquid from 

 distilling from R into D. Yet from time to time a small quantity 

 of liquid appeared on the mercury in D; however no perceptible 

 disturbance of the equilibrium between the two phases ensued, at 

 least the manometer showed no permanent change. 



In case the temperature of observation should exceed that of the 

 room the same result may be obtained by letting the water in 

 through F and by causing it to flow off through E. G may serve 

 here to prevent the level from rising too much if F for the time 

 being does not lead off a sufficient quantity. 



§ 6. The Stirring. 



The soft iron stining-apparatus consists in a little rod (long 

 15 m.m.) provided at both ends with a disc (broad 12 m.m.) and 

 moved electro-magnetically by means of a coil 6', outside the water- 

 bath. A cylinder T of sheet iron fitting round the reservoir moves 

 together with the coil and serves to concentrate the lines of mag- 

 netic force in its axis. The current for this coil is supplied by four 

 portable accumulators. 



§ 7. The analyses. 



The composiiion of the gas-mixture, received above the mercury, 

 is determined by having the carbonic acid absorbed by pieces of 

 caustic potash (cylindres of 10 to 15 m.m. length). They must not 

 bo too dry, else we are not sure that all the carbonic acid will be 

 absorbed. But on the other hand care must be taken that those 

 pieces are not too moist, as a separate experiment showed that the 

 methylchloride is dissolved by a saturated solution of caustic potash. 

 After some practice I soon succeeded in introducing potash in the 

 desired state of humidity into the gasometric tubes. 



For some days the gas is left in contact with the potash. In order 

 to hasten the absorption the tubes are plunged as far as possible 

 into deep reservoirs filled with mercury, each consisting in an iron 

 gaspipe, closed at the bottom and carrying at the top a wide glass 

 basin. The absorption of the carbonic acid may also be hastened by 

 moving the tube in the mercury up and down. 



