196 Experiments an the Production of Air 



standing ; and I shall sometimes (following the example 

 of Dr. Ingen-Housz) write this number only, in noting 

 the goodness of any air in question. 



I would just observe, with respect to the process of 

 proving the goodness of any kind of air by the test of 

 nitrous air, that I mix the two airs in a phial about i 

 inch in diameter, and 4 inches long, putting the air to 

 be proved into the phial first, and then introducing the 

 nitrous air, one measure after another, till the volume 

 of the two airs, after the diminution has taken place, 

 amounts to more than one measure and is less than two 

 measures. 



Immediately after the introduction of each measure 

 of nitrous air, I give the phial a couple of shakes ; after 

 which I suffer it to stand at rest, while I prepare another 

 measure of nitrous air, which commonly takes up about 

 20 seconds. 



The measure of the eudiometer being filled with air, 

 I suffer it to remain quiet underwater 15 seconds, or 

 while I can leisurely count 30, in order that the air may 

 have time to acquire the temperature of the water in the 

 trough, and that the water in the measure may have time 

 to run down from the sides of the glass tube ; and in 

 shutting the slide of the eudiometer, I take care to bring 

 it out to be exactly even with the surface of the water in 

 the trough. Similar precautions are likewise made use 

 of in measuring the volume of the two airs in the tube 

 of the eudiometer, after they have been mixed and dimin- 

 ished in the phial. 



In order that I may know when I have added nitrous 

 air enough to the air in the phial, so that the volume of 

 the two airs may amount to i measure, and may not be 

 greater than 2 measures, there are two marks upon the 



