LABORATORIES FOR GENERAL TEACHING 25 



other devices connected with his well-known researches on com- 

 bustion. 



The reader who is not a chemist will require some further 

 information as to what is to be found in such establishments as 

 those just described, and what sort of work goes on therein. 



Returning therefore to the main laboratory in the pure 

 chemistry department, it will be seen from the picture that the 

 working benches are arranged in groups of four over the entire 

 area. Each student is provided with a share of the table top, 

 five feet from side to side, a sink on one side, and a suite of 

 drawers and cupboards below, which provide for all ordinary 

 requirements. On the top of the table and in front of the 

 worker are shelves on which stand bottles containing the liquid 

 and solid reagents most commonly in use. There are two gas 

 taps to which the Bunsen burners employed can be attached by 

 flexible rubber tubing. The water supply is also duplicated, 

 the one tap serving for the washing of glass or other apparatus, 

 while the other is permanently connected with a high pressure 

 water pump, by which a reduced pressure or " partial vacuum " 

 may be established in any vessel connected with it. This is 

 especially useful in hastening filtration through the paper filter 

 commonly used. 



Another agent indispensable in analytical work is hydrogen 

 sulphide or sulphuretted hydrogen gas. This gas has a dis- 

 gusting smell and is very poisonous ; hence precautions are 

 necessary to prevent the escape of any appreciable amount into 

 the atmosphere of the laboratory. In the South Kensington 

 laboratory.it is generated by the action of hydrochloric acid on 

 sulphide of iron, and is collected in a gas-holder standing in oil, 

 the whole process being conducted in a chamber devoted ex- 

 clusively to this purpose, and situated in one corner of the build- 

 ing with door and window opening outwards. From the gas- 

 holder the sulphuretted hydrogen is conveyed in a system of 

 distribution pipes to each working place, where a little glass 

 cupboard, to be seen in the illustration, contains a tap from 

 which a stream of the gas may be obtained when required. This 

 glass cupboard is connected with a wide pipe leading into the 

 system of ventilation conduits situated beneath the floor, into 

 which, by the operation of an electrically driven fan in the 

 basement, the whole of the laboratories and other rooms are 

 cleared of noxious gases and supplied with fresh air. 



