CHEMICAL SCIENCE. 217 



tity of lime-water, and by ascertaining the quantity of caustic lime 

 contained in the lime-water, by means of trituration with oxalic acid. 

 In order to take a sample of the air which would remain in the iron 

 room, a sucking and pressing pump should then be connected with 

 the flue, by means of which bottles containing from six to eight litres 

 misrht be filled with air, the carbonic acid of which might be deter- 



^j cu 



mined by adding lime-water to it. The same pump would also serve 

 for ascertaining, during an experiment, the variations of the carbonic 

 acid in the current of air at different times. A contrivance should 

 also be added to this, by means of which ad libitum samples of any 

 amount could be taken, without causing a loss of air for the measure- 

 ment of the whole current. This could be done by connecting an 

 air-tight bottle with the pump, and completely replacing the air 

 originally contained in the bottle with air from the flue, by setting 

 the pump in motion for some time. The air which would have been 

 pressed out of the bottle should then not be allowed to escape into 

 the atmosphere, but should again, by means of a caoutchouc tube, 

 be conducted back to the current which goes towards the gas-meter, 

 at such a point, of course, where the measurement of the carbonic 

 acid would not be disturbed by it. In order that the current of air 

 might not carry water by evaporation from the large gas-meter, the 

 air should go, previously to entering the gas-meter, through a stand- 

 ing cylinder filled with pieces of moistened pmnice-stone. Where 

 the air leaves this latter apparatus, a psychrometer should be con- 

 nected with the flue, for measuring the temperature and the moisture 

 of the air. At the entrance into the gas-meter, a psychrometer and 

 several nozzles for tubes should be fitted in, before the pumice-stone 

 apparatus, in order to allow taking samples of air, etc. 



After Prof. Pettenkofer had communicated this plan to the presi- 

 dent of the Academy, Baron von Liebig, and some other colleagues, 

 it was laid before the Technological Committee of that body. This 

 committee made a report on it, in consequence of which King Max 

 gave four thousand florins out of his private purse for the construc- 

 tion of such an apparatus of respiration. This is the first machine 

 of its kind in which observations may be made under normal condi- 

 tions. One may live in it, as in any well-aired apartment; one may 

 take exercise, work, eat, and sleep in it, according to one's custom. 

 Food and other things may be taken in and out through a movable 

 window in the door of the room without disturbing the experiment, 

 just as we may open the door of a stove, in order to poke the fire, 

 or to take out the ashes, without having to fear an escape of smoke 

 into the room, provided there is a thorough draught in the chimney. 

 Another individual, who is outside of the iron room, to control the 

 experiment, does not, by his respiration, disturb the result in the 

 least, for the quantity of carbonic acid contained in the air which 

 enters the room is continually controlled by one of the two appara- 

 tuses, and can therefore be easily subtracted. By means of this in- 

 genious contrivance, all problems in vegetable and animal physiology, 

 as far as an increase or a diminution of carbonic acid and water in 

 the air are concerned, may be solved under normal conditions, and 

 in such an exact manner as was impossible before. 



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