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The apparatus required consists, in addition to an ordinary 
pneumatic trough, of two tubes each half-inch diameter and 
16 inches long, closed at one end. One of the tubes is gra- 
duated into 50ths of a cubic inch, and the other is coated 
internally with phosphorus. This is effected by dropping 
into the tube a few pieces oi phosphorus, it is then to be 
closed by a sound cork, and the phosphorus (melted by 
immersing the tube in hot water) may be spread in a thin 
coating over the interior by turning it round as it cools. 
On cooling, the cork is to be withdrawn, the tube filled with 
water, and a piece of indiarubber tube tied securely over the 
mouth. This completes the apparatus. 
Modus Operandi : — Both tubes are filled with water and 
allowed to remain in the trough, a portion of the air to be 
examined is passed into the measuring tube, which is now 
allowed to remain for five minutes in the trough to allow 
it to attain the same temperature as the water. It is lifted 
until the water is at the same level within and without, and 
may then be closed by the finger, and withdrawn from 
the trough. The volume is easily noted. This done, it is 
connected by the indiarubber joint with the phosphorus 
tube, into which the air is allowed to flow. The whole 
may now be placed for half an hour in the trough, when 
the gas may be poured back into the measuring tube, the 
level once more taken, and the volume read off in the same 
way as before. The loss is oxygen. 
a Measuring tube. 
b Indiarubber junction. 
c Phosphorus tube. 
No claim is made for strict scientific accuracy in con- 
nection with this apparatus ; its sole merit consists in its 
offering an easy and rapid means of approximately deter- 
