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T H E JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY
Vol. 13, No. 2
LABORATORY AND PLANT GASOLINE FROM NATURAL GAS. V-HYDROMETER FOR SMALL AMOUNTS OF GASOLINE By R. P. Anderson and C. E. Hinckley UNITED NATURALGAS Co., OIL CITY, PENNSYLVANIA Received October 15, 1920
I n testing natural gas for gasoline it is important t o determine the gravity of the gasoline obtained. When t h e quantity of gasoline is insufficient t o float t h e extremely small hydrometers t h a t are available for this purpose, it is convenient t o possess an instrument which requires but 4 cc. of gasoline for a gravity determination. Such an instrument is It is a modification of shown in Fig. I . hydrometers Nos. 4060 and 4072 of Eimer and Amend's 1913 catalog, and may be ordered from this firm. The instrument is designed for immersion in water at 60" F., and when t h e bulb B is filled t o t h e mark with gasoline a t 60" F. t h e gravity of t h e gasoline is obtained directly from t h e position of t h e hydrometer in t h e water, t h e stem being calibrated from 60' t o 100' BB. A study of t h e effect of temperatures other t h a n 60' F. upon t h e reading of t h e instrument discloses t h e fact t h a t t h e temperature correction is small as compared with t h a t necessary in t h e case of t h e ordinary hydrometer. This is because t h e contraction or expansion of t h e gasoline with change of temperature is partially compensated for by the corresponding contraction or expansioninthe water in which t h e hydrometer is immersed. The relationship between t h e contraction (or expansion) of the gasoline and t h a t of t h e water is shown graphically in Fig. 2 . The three, straight, diagonal lines picture t h e change in weight of 4 cc. of gasoline of three different temperatures.1 T h e curved lines show t h e change in weight of 23 cc. and 47 cc. of water for t h e same temperature range.2 Twentythree cc. represent the proper volume of the hydrometer up t o t h e 80' BB. mark in FIG.1 order t h a t t h e most complete temperature compensation may be obtained between 50' and 70' F., and 47 cc. represent a hydrometer volume which gives excellent compensation at the temperature of t h e maximum density of water. The actual error in hydrometer reading resulting from incomplete compensation may be computed for any given conditions of temperature, gravity of gasoline, and hydrometer volume as shown in Table I. T h e effect of t h e expansion or contraction of t h e hydrom1 The change in weight of 1 cc. of 60° BB. gasoline for 1' F. is taken as 0.00045 g.; for 1 cc. of 80' €36. gasoline, 0,0005 g . ; and for 1 cc. of 100° BB. 12 (1920), 1011. gasoline, 0.00055 g. See THIS JOURNAL, 2 Data on change of density of water with change of temperature taken from Smithsonian Tables, "Handbook of Chemistry and Physics." 7th Ed., p. 322.
eter with change of temperature upon t h e degree of compensation is too small t o need consideration in this connection. TABLE:I-HYDROMETER COMPENSATION (Hydrometer Volume 23 Cc., Gravity of Gasoline SOo Be.) Change in Weight Uncompensated Change ,--------of---------in Weight-Error Temp. Gasoline Water Per Cc. Degrees ' F. (4 Cc.) (23 Cc.) Total of Gasoline Baume 50 +0.0200 +0.01587 +0.00413 +O 00103 -0.32 55 4-0 0100 $0.00890 +0.00110 +0.00027 -0.08 65 -0.0100 -0.01109 +0.00109 +0.00027 -0.08 70 -0.0200 -0.02401 +0.00401 +O.OOlOO -0.31
Computations of t h e sort illustrated in Table I have been made for three grades of gasoline (60°, go', and 100' Be.), for temperatures from 3 2 ' t o 7 0 ' F., and for hydrometer volumes of 23 and 47 cc., and t h e results are shown in graphical form in Fig. 3. An error of +I" BB. as used in this figure means t h a t I O BB. must be subtracted from t h e observed hydrometer reading t o obtain t h e gravity a t 60' F., and with an B8., I " BB. must be added. Fig. 3 error of -I' may thus be used in correcting observed Baume gravities t o a temperature basis of 60' F.
FIG.2
It will be noted from t h e figure t h a t t h e hydrometer with a 23-cc. volume may be used for gravities from 60' t o 100' BB.,over a temperature range from 50° t o 70' F., with a maximum correction of 0.6' BB. This portion of t h e figure is ruled t o I ' F. and 0.1" B6. for convenience in applying corrections. I n t h e case of t h e hydrometer with a 47-cc. volume, t h e most desirable temperature range is from 36' to, 40' F. It may be used from 37' t o 40' F. with a maximum correction of =t0.6' BB. At 35.7' F., t h e correction is zero for 60' BB. gasoline; for 80' BB. gasoline t h e temperature for zero correction is 37.7F., and for 100' B6. gasoline, 39.7' F. T h e 47-02. hydrometer is t h e desirable one t o employ in obtain-
Feb., 1921
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 C H E M I S T R Y
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tive manner a t least, certain qualities and characteristics of fixed oils. T h a t the test is unsatisfactory has long been recognized by various observers, and t o do away with this error, Martens, in a paper which was abstracted in the Journal of the Society of Chemical I n d u s t r y in 1890, recommended t h a t a U-tube be used in a freezing mixture and connected with air pressure, t h e temperature a t which the air begins t o flow under these conditions being taken as the cold test of t h e oil under investigation. I n an attempt t o improve t h e application of methods which would show t h e lowest temperature a t which oils will flow, many of t h e suggested schemes were tried. Since the one described by Martens seemed t o be t h e most promising, t h e apparatus which is t h e subject of this paper was devised. Results can be obtained within 0.25' F. or less, depending upon t h e thermometer, and t h e personal error is t o all intents and purposes nil.
FIG.3
ing t h e gravity of gasoline condensed and collected at temperatures not much above 3 2 ' F., since, under these conditions, warming t o 60' F. would involve a considerable change in gravity as a result of evaporation of t h e more volatile constituents. It will be noted also t h a t t h e 47-cc. hydrometer may be employed between 36' and 6 6 " F. with a maximuni correction of * 1.0"BB. SUMMARY
I--A hydrometer has been described which makes possible t h e rapid and fairly accurate determination of t h e gravity of gasoline when t h e quantity is insufficient t o float t h e usual type of hydrometer. Only 4 cc. of liquid are necessary. +-The magnitude of t h e corrections necessary t o change observed gravities t o a 60" F. basis depends upon t h e volume of t h e hydrometer. A chart has been prepared t o be used in making corrections for hydrometer volumes of 23 and 47 cc. The desirable range of temperature for t h e hydrometer with a volume of 23 cc. is from 50' t o 70' F., and for t h e hydrometer with a volume of 47 cc. from 37' t o 40" F. The maximum error for t h e 47-cc. hydrometer over a range from 36 ' t o 66 F. is * I ' B&, and consequently, for approximate work, the correction may be omitted entirely. A COLD TEST APPARATUS FOR OILS By G. H. P. Lichthardt SOUTHERN PACIFIC RAILROAD CO., SACRAMENTO, CALIFORNIA
Received September 27, 1920
The apparatus herein described for making the cold test is t h e result of an attempt t o eliminate, as far as possible, t h e personal equation in this useful test which has long been used t o shorn, in a compara-
The apparatus consists of a refrigerator tank, B, containing nine tubes of glass, 0.3 in.-inside diameter, which are bent a t one' end and are connected with t h e air supply H. The cooling box is of galvanized iron and square in shape, t h e dimensions being 6 X 6 X 6 in., and contains t h e freezing mixture which consists of acetone and carbon dioxide snow. The mechanical stirrer C, operated b y t h e motor D, insures uniform temperatures throughout. The readings are taken from a low-temperature thermometer, F, and t h e air pressure is regulated b y t h e glass t u b e inserted in t h e water contained in t h e jar A. The test is applied b y placing enough of t h e oil under investigation in t h e t u b e to occupy 6 in. of t h e tube length, after which t h e freezing mixture
