IiVDUSTRIAL AND ENGINEERING CHEMISTRY
June, 1923
chart a t 60 degrees and assumed to be the curve of saturated steam. For each temperature division the corresponding pressure was found from the Marks-Davis steam table, marked upon the steam curve, and this point projected across to the temperature scale. This gave a complete temperature scale ranging from 32’ to 700” F., entirely arbitrary but serving the purpose. The source of the data from which the curves are drawn is indicated by letters.2 The heavy lines are transferred from curves. Single points given are indicated by circles, extensions by lighter lines. The agreement by different authorities is best for pentane, so this line was extended through the critical point and assumed to contain the point of convergence. The heavier hydrocarbon curves were extended to intersect the pentane line, and it was found that the intersections were so close that a median point could be chosen and all the extensions drawn to this point. It will be noted that the error, if any, in so constructing the chart, is less than the probable 2
Wr-Woringer,
”Engineering Thermodynamics,” Lucke, p. 485.
S- -Sore1 Ibid. ~
Y-Young, I b i d . I,--Lucke, I b i d . Ws-Westcott, ”Handbook of Xatural Gas,” Table 12. G--Goodenough, “Mechanical Engineers’ Handbook,” Marks, p 323. D--Landolt-Bomstein, “Tabellen” (1905), Dewar. Z--Ibid., Olszewski.
595
experimental error as indicated by the divergence between different authorities. This chart, of course, is not presumed to supplant experimentally derived curves or even to serve as a check, except roughly, upon such data, but is merely offered as a convenient means of readily deriving closely approximate values from a single boiling point where no other data are available. For this purpose, the advantage of straight lines is obvious. For instance, the boiling points of hydrocarbons CNHU and over are usually determined for 15-mm. mercury pressure, since the boiling points a t atmospheric pressure are above the cracking temperature. These points may be imerted on the 0.29-lb. line and the complete curve drawn. Moreover, the lighter fractions, such as ethane, propane, etc., cannot exist as liquids a t the ordinary distilling temperatures and saturation vapor pressures cannot be directly determined for temperatures beyond the critical. However, they can exist a t these temperatures in solution with heavier members of the series in what may properly be caIled the liquid phase, and by extending the curves a fair estimate may be made of the pressures they exert under these conditions and their partial pressures calculated from RaouIt’s law. In this way it is hoped that the chart may be of material assistance in solving many problems in petroleum distillation, fractionation, and gasoline absorption.
Apparatus for the Alpha-Naphthol Test for Sucrose’ By Guilford L. Spencer THECUBAN-AMERICAN SUGAR Co., N E W Y O R KN. , Y.
The cy-naphthol test is of importance in sugar factories in detecting traces of sucrose and in locating the sources from which they are derived. In a well-conducted factory the test is made with such frequency that apparatus of greater convenience than the usual pipet and test tubes becomes desirable. Furthermore, there is always danger of the usual tubes becoming contaminated with sugar, through haste or carelessness, and thus sugar may be indicated when none is present in the sample. The essential conditions for a suitable apparatus are safe and convenient storage of reagents and a test tube that may be thorouglily cleansed without risk of contamination with sugar-which always is a danger in a factory laboratory. The apparatus described here was used during one manufacturing season in a large factory and was then modified to correct slight defects, and is now in constant use in five factories. I n the larger factories the day and the night assistant is each supplied with an apparatus and each is held responsible for the proper use of his own. The apparatus is shown in the illustration. The small container is for a 20 per cent solution of a-naphthol in alcohol and holds about 35 ml. The large vessel is for pure, concentrated sulfuric acid and has a capacity of about 250 ml. If the acid is not colorless, it should be heated to the boiling point and cooled before filling the vessel. The stoppers have small inlets for air, which should be nearly closed. The threeway cock and shell are marked for position with colored glass. The outlet connects with the waste jar through rubber tubing. Distilled water is led through rubber tubing to near the funnel tube for washing it, and should be provided with a nozzle and bead valve. The apparatus is enclosed in a 1
Received April 20, 1923.
few seconds are allowed for djffusion, and then the three-way cock is manipulated to back up the sulfuric acid to about 5 mm. above the bottom of the. funnel tube. If sucrose is
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