ON EUDIOMETERS. 295 



tht annoyance which is produced when in the middle of a 

 complex analysis you see an abominable bubble of air rising 

 up through the mercury in the eudiometer and mixing with 

 the gas. Of this I have had several experiences, which made 

 me vow I would never use steel joints when I could do 

 without them. In a glass joint you can see immediately 

 when anything goes wrong, whereas it is quite impossible 

 to find where any part is out of order in a steel one. 



Quite recently an apparatus has been described by Von 

 Jolly, known as a constant eudiometer because he uses 

 a constant volume. In Frankland's apparatus 1 told you 

 there were eight or ten divisions of the tube by which the 

 volume of gas was to be measured \ but in Von Jolly s 

 you have one only. In order to get rid of the tempera- 

 ture corrections Von Jolly employs a reservoir of ice placed 

 round the vessel, and in this way you have only the 

 barometric correction remaining. This barometer tube, at 

 the top of which is the measuring vessel, is connected by 

 means of a flexible connector with another tube capable 

 of being slid up and down on the stand, so that by raising 

 and lowering this, first roughly by means of this wooden 

 screw and afterwards by a fine adjustment, you bring the 

 level of the mercury absolutely to a level of the fiducial 

 point at the bottom of the measuring vessel. There is one 

 suggestion I would make to Professor Von Jolly, and that 

 is to simply convert the open tube into a barometer, and 

 you would have all the corrections complete at once. 



There are many processes in manufacturing chemistry 

 in which gases can be conveniently analysed, and there are 

 on the table five or six different pieces of apparatus which 

 are applied for these purposes. Here is one which has lately 

 come into use, invented by Dr. Scheibler. It is an apparatus 

 for the estimation of calcic carbonate in bone charcoal, and 

 for the analysis of carbonates in general. A we ; ghed 

 quantity of the substance is submitted to the action of 

 hydrochloric acid in a bottle connected by a caoutchouc 

 tube with the measuring apparatus. The level in the two 

 tubes is adjusted by introducing a liquid or allowing it to 

 flow out. By graduating the tube in a different manner 

 and by using a constant quantity of the carbonate you can 

 determine the percentage of the carbonate instantaneously. 

 Then there -is an apparatus of Dittrich perfectly similar 



