FOR DETERMINING SMALL AMOUNTS OF CARBON DIOXIDE 369 
The volumetric apparatus which has been developed by the writer has 
the advantages of being light, easily portable, measuring only 14x4 inches, 
and so simple in construction that it can be used by an unskilled operator. 
The apparatus is made entirely of glass and mounted on wood, and makes 
determinations ranging from o.i to 3.0 per cent. The calibrations, however, 
are sufficiently far apart so that readings by interpolation may be made to 
0.05 percent. The apparatus can readily be used in the close, cramped 
quarters and poor light often found within storage rooms. Each deter- 
mination takes from three to five minutes. 
The carbon dioxide apparatus described herewith (see figure i) consists 
of a bulb A and stem B of about 150 cc. capacity, a stopcock E, a balance 
tube C, a two-way stopcock D, and a funnel F. The apparatus is filled 
with air to be analyzed, and sodium hydroxide is introduced to absorb 
the carbon dioxide which is replaced by water entering from the balance 
tube C. The height of the column of water in the tube B gives directly 
in percentage the amount of carbon dioxide removed from the sample of air. 
Following is a description of the method of operating the carbon dio;Kide 
apparatus. Wet the inside of bulb and stem B, then drain one minute.' 
Fill the balance tube C with water. The water should rise in the balance 
tube just to fill the bore in stopcock D. Be sure no air bubbles are left inside 
the rubber tubing. Turn the stopcock D to make connection with the 
outlet G. Open the stopcock E, and by means of a bulb attached at G, 
pump into the apparatus sufficient air to get a representative sample, or 
place the mouth over G and draw through the apparatus sufficient air to 
get a good representative sample within. Turn D to connect with C. Lower 
the balance tube C till the level of water within is slightly below the bottom 
of tube B. Partially fill funnel F with a saturated solution of sodium 
hydroxide. Allow this to enter the apparatus slowly. Close E and raise 
the balance tube to allow two or three cubic centimeters of water to enter 
tube B along with the sodium hydroxide, then close D and tip the apparatus 
to allow the liquid to run into bulb A . Shake gently to allow the liquid 
to splash about in bulb A to facilitate absorption of carbon dioxide. Turn 
the apparatus upright. Open the stopcock D to connect with the balance 
tube C. Raise and lower the balance tube C as far as possible five or six 
times to force the rapid diffusion of sodium hydroxide, thus making the 
liquid in C of uniform density throughout. Allow liquid to drain down 
from the side of the apparatus for one minute, then hold the balance tube 
so that the top of the column of liquid within is on a level with that in tube 
B — thus correcting for atmospheric pressure. Read the height of liquid in 
tube B. (Because of the unequal capillarity due to the difference in diam- 
eters of tube B and the top of leveling tube C, when making a reading hold C 
so that the top edge of the meniscus is on a level with the bottom of the 
meniscus in B.) The reading gives directly in percentage the amount of 
carbon dioxide originally present. Rinse out after each determination. 
