V O L U M E 26, NO. 3, M A R C H 1 9 5 4
49 1
over a period of 97 hours and the average deviation between the Orsat and the mixture ratio analyzer was found to be o.13Y0carbon dioxide in nitrogen a t the point tested. The analyzer exhibited a drift of about 0.1% carbon dioxide in nitrogen in 2-1 hours of continuous operation. The mixture ratio analyzer has been used on many different types of engines. Figure 9 shows selected portions of a continuous recording of an engine mixture ratio analysis. The engine speed, throttle setting, and mixture ratio were held constant for this test. Orsat analysis of the exhaust gas was in close agreement with the mixture ratio analyzer results except for a few points. It is difficult to obtain an Orsat sample which is representative of a particular point on the recording. Figure 10 shows a typical recording of the analysis of the exhaust gas from a single cylinder laboratory engine. The large variations in mixture ratio were not detected or suspected before a recording was made of the exhaust gas. The fault lay in the carburetor design and a slight modification greatly improved the mixture ratio. ACKNOWLEDGMENT
The author wishes to express his appreciation and thanks t o
E. J . Martin, F. W. Chapman, and the late W. S. Erwin for their helpful and stimulating discussions. LITERATURE CITED
R. W., and Barlow, G. E., Australian J . Sci. Research, 1 , NO. 2, 176-89 (1948). (2) Crouthamel, C . E., and Diehl, Harvey, ANAL.CHEW,20, 515 (1) Abbey,
.54m*
OYI
Figure 9. Selected Portions of a Continuous Recording of Engine Exhaust Gas
(1948). h so1 I I * r
OW”
Figure 10. Single-Cylinder Laboratory Engine
(3) D’iilleva, B. A., and Lovell, W. G., S A E J o v m Z , 38, No. 3, 90-6 (1936). (4) Gerrish,‘ H. C., and Meem, J . L., Jr., S a t l . Advisory C m m . Aeronaut. Rept. 757 (1943). (5) Mikelson, W., U. S. Patent 2,283,750 (May 19, 1942).
.
RECEIVED for review July 15, 1953. Accepted November 16,1963.
verts the cupric oxide to copper. After the analyzer has operated a short period on either rich or lean mixtures it is then possible to analyze exhaust gases which are a t or near theoretical optimum mixture ratios. METHOD OF CALIBRATION
The most reliable method of calibrating the analyzer is to use a com ressed gas mixture of known composition obtained from Ohio 8hemical Co., Cleveland, Ohio. This gas, of approximate specified composition, is furnished in convenient containers and must be analyzed with an Orsat analyzer before use. At least five analyses should be made in order to obtain a good average of the gas. Two tanks of gas, one to check low concentrations and one for high concentrations of carbon monoxide in nitrogen, have been found sufficient. When the analyzer has been warmed up with a fresh charge of cupric oxide, the calibrated gas is passed through the analyzer at the same flow rate that is used in analyzing exhaust gas. The gas is allowed to flow long enough to give a steady reading before making adjustments. The zero set and sensitivity are adjusted in order to bring the analyzer into calibration. After calibration, the unit is ready for operation. I t has been found that the zero setting must be checked each time the analyzer is to be used. This requires the use of only one test gas. The sensitivity or spread adjustment needs checking about once each week of continual operation.
Spectrophotometric Determination of Cholesterol And Triterpene Alcohols in Wool Wax -Correction In our recent publication of the above title [+&SAL. CHEY.,25, 149i-9 (1953)l the wrong equations were given for Methods I and I1 under the heading “Calculation of Results” on page 1499. The correct equations are as follows. Method I. Free Alcohols. Cholesterol, weight % =
loo(as30aL -
Triterpene alcohols, weight
UCUL
70=
lOO(a5.oac - ae3oac’) a C a~ ac‘aL‘
Method 11. Esters.
Triterpene alcohols, weight % = 100(assoac a C a L -uc,uL, a6aoaC’)
FRAXCIS E. LUDDY ARTHURTURNER, JR. JOHN T. SCANLAN
RESULTS
An Orsat analyzer was used to check the gas from the mixture ratio analyzer and the results from the Orsat were compared with the readings obtained from the mixture ratio analyzer recorder During an extensive and thorough test, 116 analyses were made
U550UL’)
- UC’UL’
Eastern Regional Research Laboratory U.S. Department of Agriculture Philadelphia 18, Pa.
