July 15, 1931
INDUSTRIAL AND ENGINEERING CHEMIXTRY
controlled. This apparatus consisted of a condenser of soft glass having a spiral inner tube through which water of any desired temperature could be circulated. The gasoline was contained in the outer jacket' into which was sealed a thermometer. The gasoline quickly attained and held the temperature of the circulating water. The results of tests on a sample of vapor-phase refined cracked gasoline a t three temperatures are given in Table 111. of T e m p e r a t u r e on Discoloration of Gasoline i n Sunlight COLORAFTER 15 HRS. EXP. TO SUNLIGHTGUM. COLORAFTER AND 24 HRS. STEAMOXALICACID IN 15 HRS. EXP. STORAGE OVEN DECOMPOSED~ TEMP. TO SUN LIGHT^ DARK TEST 0.001 M 0.0005 M
Table 111-Effect
53 77 96 Q
b
2.3 37 21 1gL/2 37 20 18'1'2 3,6 191/2 181/2 37 The gasoline prior to exposure had a color of 25. 15 hours.
20.7 20 7 20.7
From these results it will be observed that for this particular gasoline the effect of temperature on discoloration in the sunlight was not of any great importance. It cannot be assumed, however, that such will be the case for all gasolines. For strictly comparable results, therefore, information relative to the effect of temperature on any gasoline should be obtained before attempting a comparison of sunlight colorstability tests made a t different temperatures. The importance of this in comparing tests made in visible pump bowls in the winter and summer is obvious. Effect of Storage o n Gasoline Exposed to Sunlight Another point of interest in connection with the discoloration of gasoline in the sunlight is that such discoloration when once started continues to get worse during subsequent storage in the dark. I n Table 111 some results indicative of this fact are given, and in Table IV will be found additional
281
data illustrating this point. The three tests were made in sunlight of different intensities. T a b l e IV-Effect of Exposure t o S u n l i g h t Followed by Storage i n Dark on Color of Vapor-Phase Refined Gasoline of 25 Colors COLORAFTER COLOR E X P . AND OXALICACID IMMEDIATELY 24 HRS. STORAGE TEST DURATION DECOMPOSEDAFTER E X P . I N D.4RK 1 2 3
Hours
Mg.
6 .5 5
25.2 17.6 11.3
21 22 24
l8V2 19 20
It is iecogniaed that the distribution of spectral energy of sunlight is highly variable, and that for strictly comparable results filters should be used such that only that portion of the light which is completely absorbed by both the actinometer and gasoline is utilized (1). The accuracy of reading the color on the Saybolt chromometer, however, is not sufficient to justify such a refinement. The following precautions should be observed: The containers for the actinometer solution and for the gasoline should be of the same general character of glass, The actinometer solution should be titrated immediately after exposure, as the decomposition of the oxalic acid progresses to a slight extent in the dark after having been exposed to the sunlight. The color should be taken on the gasoline immediately following exposure or at some specified and constant time thereafter, since the discoloration started in the light continues to occur to some degree in the dark. Tests on the stability of gasoline to sunlight should, when possible, be completed in a single day. When this is not possible or desirable, fresh actinometric solution should be used on the second day and the total exposure be determined by the sum of the amounts of oxalic acid decomposed on the first and second days. ; Literature Cited (1) Leighton and Forbes, J . Am. Chem. Soc., 62, 3139 (1930). (2) Mathews and Dewey, J . Phys. Chem., 17,216 (1913).
All-Glass Steam Distillation Apparatus for Analytical Purposes' Victor E. Wellman THEB. F. GOODRICH COMPANY, AKRON,OHIO
H E necessity of determining precisely small amounts T of aniline present in mixtures of various compositions whose other constituents were non-volatile with steam, led to the development of the one-piece all-Pyrex glass apparatus shown in the accompanying diagram. The steam-distillation flask, B , has a steam inlet, A , sealed into it a little to one side of the true bottom. Flask B is tilted to prevent any froth which may form (as often happens with alkaline solutions) from climbing easily into the Hopkins distillation head, C. The delivery tube from C is sealed to a safety bulb, D , which is placed at the top of the condenser tube, E. The sample is introduced into B by means of a small-stemmed funnel placed in A. I n case the material is a solid, it may be dissolved in some low-boiling solvent, such as alcohol, and introduced in solution form, or may be powdered and flushed into B with water. Steam is then admitted through A , and if necessary the distillation is furnished additional heat from a burner, G. The distillate is collected in any suitable receptacle, such as beaker F , which may be cooled if necessary. In the particular work mentioned above the mixture containing aniline was introduced into the flask, after which an excess of sodium hydroxide solution was admitted through A . The steam-distilled aniline was collected in a beaker of dilute hydrochloric acid. The entire apparatus was 1
Received March 13, 1831.
clamped to one ringstand, making it possible to remove the residue quantitatively from the distillation flask by tilting the stand so that the liquid flowed from A.
A
Diagram of A p p a r a t u s
The apparatus will be found useful in quantitative work particularly, and generally whenever the distillate is of such nature as to prevent the use of corks, metal foil-covered corks, or rubber stoppers in the neck of the distilling flask.
