30 MM. Pettenkofer and Voit on the Elimination 



The receivers for acid, formed of an alloy of lead and anti- 

 mony, stand without change a pressure of five to six atmospheres, 

 while the charge to which they are exposed never exceeds one 

 atmosphere. There is no doubt that they can resist for a num- 

 ber of years the attack of sulphuric acid ; it covers them at once 

 with a coating of sulphate, which almost entirely prevents any 

 further erosion. 



The pump, which is made of copper, is protected against the 

 action of sulphurous acid, always disengaged from acid recently 

 introduced, by an arrangement which constantly and necessarily 

 keeps its sides coated with oil : this, so far from hindering its 

 work, makes it as perfect as possible. The valves are moved 

 mechanically, and cannot get out of order. 



These arrangements furnish apparatus which can retain a 

 vacuum for many months, and produce 2 or 3 kilogrammes of 

 ice for a kilogramme of acid at 66 degrees, which is only taken 

 out when dilution is reduced to about 52 degrees. Freezing 

 generally commences three or four minutes after exhausting ; if 

 cold water of 3 or 4 degrees is wanted, two minutes are sufficient; 

 and agitation for a few seconds restores the air it has lost in 

 vacuo. 



Besides sulphuric acid, which is the most economical agent, 

 various hygrometric substances may be used, among which 

 caustic potash and soda are distinguished by the intensity of the 

 cold they produce. 



Von Pettenkofer and Voit* have made a series of experiments 

 on the elimination of carbonic acid, and the absorption of oxygen 

 in the waking state and during sleep. These experiments were 

 made by means of the apparatus of which a brief account has 

 already appeared in this Journal f . They made determinations of 

 the products of respiration, which exhibit a great difference be- 

 tween the respiration of a man working and resting, and between 

 a man in the waking and in the sleeping state. The subject of the 

 experiments was a powerful working man, 28 years old. During 

 the day of rest and of work he had exactly the same food, with 

 the exception that when he was at work 600 grms. more of water 

 were consumed. The numbers obtained are given in the fol- 

 lowing small Table : — 



* Munich Academy, November 10, 1866. Zeitschrift der Chemie, Ja- 

 nuary 1867- 



f 'Phil. Mag. S. 4. vol. xxi. p. 544. 



