Jan., 1916
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
A RAPID METHOD FOR THE DETERMINATION OF
CARBON DIOXIDE' B y W H. WAGGAMAN Received July 2, 1915
All t h e present methods for t h e determination of carbon dioxide require either considerable time or else t h e close attention of t h e analyst throughout t h e operation. The following method should prove useful for commercial a n d certain other purposes, as t h e apparatus runs automatically a n d t h e analytical results can be obtained quite rapidly. The apparatus is very similar t o t h a t usually employed in such determinations. The train of absorption bulbs differs little from t h a t described by Cameron a n d Breazeale;z t h e final member, however, consists of a tube containing barium hydroxide t o indicate a n y loss of carbon dioxide due t o too rapid passage of t h e gas through t h e apparatus. This bulb also proves of value in showing a t once t h e exhausted condition of t h e potash absorption bulb. I n t h e usual method for t h e determination of carbon dioxide most of t h e time is consumed in heating t h e acid solution in order t o drive off t h e last portion of t h e carbon dioxide, a n d care must be taken during the operation lest too rapid heating should cause t h e liquid t o rise in t h e tube through which t h e current of air should enter, a n d t o pass over into t h e auxiliary flask containing potash. Should this happen the whole determination is lost. The use of a small flask (100 or 150 cc.) for t h e decomposition of t h e carbonate or organic compound has been recommended, since this does away with the large air space above t h e liquid. During preliminary experiments, however, i t was found t h a t t h e sudden expansion of gas confined in a small flask causes more trouble t h a n in a larger flask where t h e
41
In t h e accompanying figure, A represents the flask in which t h e decomposition takes place, and is surrounded by t h e coil K of lead tubing. The gas evolved passes through t h e condenser C, inclined upwardly, through t h e capillary t u b e leading t o the train of absorption bulbs. This train consists of t h e following: E, containing a solution of silver sulfate t o remove a n y chlorine or hydrochloric acid; F, containing concentrated sulfuric acid t o absorb water vapor; G (weighed before a n d after t h e operation), containing a strong solution of potash and attached to a tube, H, containing calcium chloride; I , containing concentrated sulfuric acid t o prevent water vapor from passing back into G ; and L, containing a saturated solution of barium hydroxide. Air is drawn through the solution of potash in t h e flask M and through t h e tube N passes below t h e surface of the liquid in A. P a r t of t h e U-tube of t h e regulator 0 is filled with mercury, t h e tube X being raised or lowered for regulation. A pilot flame, Q , lights t h e burner P, whenever t h e gas comes on. I n Table I are given the results obtained with two samples of calcium carbonate in which t h e quantity of carbon dioxide was determined by blasting a sample t o constant weight. TABLEI-ANALYSES OF T W O SAMWLBS O F CaCOs Weight of CaCOs employed for analysis = 0 . 5 gram RESULTS BY BLASTING Sample I Sample I1 0.2190 g. Weight of COz in 0 . 5 g. CaCOj 0.2195 g . 43.80 43.90 Per cent COz in sample ANALYSES BY AUTHOR'SMETHOD RESULTSON SAMPLE I1 RESULTSO N SAMPLE I TIME COa FOUND TIME Con FOUND Min. Gram Per cent Min. Gram Per cent Over60 0.2178 43.6 60 0,2180 43.6 Over 60 0.219.5 43.9 Over60 0.2175 43.5 60 0.2195 43.9 Over60 0.2185 43.7 60 0.2175 43.5 Over60 0.2170 43.4 43.76 60 0.2170 50 0.2188 43.4 45 0.2175 43.5 30 0.2175 43.5 45 0.2175 43.5 43.8 30 0.2170 43.4 45 0.2190 45 0.2190 43.8 30 0.2185 43.7 40 0.2175 43.5 40 0.2185 43.7 30 0.2178 43.6
This method may also be employed for the rapid estimation of carbon dioxide in t h e organic matter of soils and in other organic compounds. Table I1 TABLEI1 Weight taken COz found SUBSTANCE FORMULA Gram Gram
U
FIG.I-APPARATUS
FOR
RAPIDDETERMINATION OF CARBON DIOXIDE
mean temperature of t h e gaseous mixture is lower.
A 300 cc. Erlenmeyer flask was finally employed, and it was kept cool b y a coil of lead tubing through which cold water flowed. The cooling shortened t h e time required for t h e operation b u t did not do away with t h e necessity of watching t h e apparatus continually. By means of a n Ostwald regulator t h e flame under t h e flask was regulated automatically, so t h a t t h e heating would decrease as t h e pressure in t h e flask increased a n d vice versa. 1
Published by permission of the Secretary of .4griculture. A m . Ckem. Soc.. 26 (1904), 29.
2J.
Per cent recovered 98.83 99.16 Sugar C12H2~011 99.55 99. Urea CHaNzO .. R7 99.18 100.85 Asparagine C~HBNZOJ.HZO 98.81 C~QH~NHP hTaph+yl97.3 1( a ) amine 99.02 Sulphanilic CsHvNSOs 99.11 ( b ) 99.57 acid ( a ) Some volatilized. ( b ) Potash bulb became exhausted
gives t h e results obtained on some known organic compounds. Since several of the substances decompose with great rapidity, some care was taken during t h e addition of acid, after which t h e action subsided somewhat and t h e regulator rendered further attention unnecessary. Forty minutes was found t o be sufficient time for the determinations, although many were run for a full hour. BUREAUOF
SOILS
WISHIKGTON,
D.
c.
