64 Royal Society : — 



clip E. Through the stopper of B is a siphon, F, the long limb of 

 which is cut and joined with caoutchouc tubing, which can be closed 

 by the chp G. Through this stopper is a third tube, H, connected 



by caoutchouc with the tube I ; this can be closed by the clip K. 

 The tube I is about 3 feet long, and goes into the vessel L, which 

 is partly filled with water. 



The water to be distilled is mixed with solution of potash and 

 permanganate of potash, and placed in the flask A*. Before distil- 

 lation is commenced, a rapid current of pure hydrogen, or some 

 other gas, must be passed through the apparatus by the tube C to 

 displace the air and carry off all the germs the air may have contained. 

 The clip G is first left open, then this closed and the clip K opened, 

 which allows the gas to pass through the water in the vessel L. 



The gas should be passed through for about fifteen minutes. The 

 clip E is then closed, and the distillation carried on. When the opera- 

 tion is complete, the gas must be again passed through the appa- 

 ratus, and the connexion with the tube I broken by closing the 

 clip K. The water is drawn off through the siphon F. The long 

 tube acts as a safety-tube, and is made so long that the absorption is 

 noticed in ample time to close the clip before any air can enter through 

 that tube. 



The water has to be redistilled three or four times before it is ob- 

 tained free from germs, and must be kept in the apparatus in which 

 it is distilled until wanted, to prevent any contact with air. 



Some water which had been distilled on the 20th of November, 



* The reasons why I employed permanganate of potash (in large excess) were 

 that under the influence of heat its oxidizing powers were much increased, and 

 that it gave off no gas that could interfere with the purity of the water, this salt 

 in solution not even yielding oxygen under any circumstances. 



