I N D U S T R I A L A N D ENGINEERING CHE-XISTRY
July 15, 1930
Figure 3-Finished
Per Cent C h a r t for Midcontinent Crude
ease with ~vhiclithe gas oil would crack and of the knock rating on the resulting ga:-0 1'me. Paraffin-distillate and lubricating-oil yields are again essentially thoqe obtained in pipe-still rather than shell-still equipment. The quality of the lubricating oil obtainable can be closely estimated froni the viscosity-temperaturegravity relationship shown in the work-up chart, the temperature being indicative of the flash to be expected. The method, as outlined above, of estimating the viscosity of any part of a crude by reading the value a t its mid-point has proved exceedingly useful. The accuracy of this method is not impaired by the width of the cut in question or the type of equipment on which it is to be made, provided only that the fractionation is the same a t both ends of the cut and that no cracking is done. The gravity is also accurately estimated provided the cut is not too wide.
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The maximum amount of pressable distillate obtainable from a mixed-base crude when operating with good fractionation and no cracking can be closely approximated by considering the upper end of the cut to be limited to a n average of the 870" F. (465.5" C.) and 600 viscosity points on the work-up. The yield is then obtained b y doubling the difference between this point and that a t the desired sriscosity. For a paraffinbase crude the cut temperature is usually somewhat higher. The bottoms obtained are again essentially those obtained in equipment giving no cracking. The molecular weight of any cut on the crude can be closely approximated by the following procedure : First, the temperature corresponding to the mid-point of the cut is read off the final chart. Then the molecular weight of the paraffin hydrocarbon corresponding to this teniperature is obtained and multiplied by 0.95 to give the molecluar weight of the cut. It is obvious that if the cut is very Tvide it should be split u p into two or more equal portions, each one of these treated separately as above and the molecular weight of the n-hole calculated from the parts to insure accuracv. Sormally this method gives results accurate to nithin 5 per cent. Since this method gives a true-boiling-point curve of the crude, it is possible to calculate closely the temperatures required to remove any portion from the crude or reduced crude by operation either in shell or pipe stills. Details of thiq calcnlation are given bv Piroornov and Beiswenger (31 and Pirooinov and Loomis (.$). Y
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Literature Cited
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Calingaert and Davis. ISD. EKG.CHEM.,17, 1287 (192.5). Cox, I b i d . , 15, 592 (1923). Piroornov and Beiswenper. I . .Im. Petroleum Inst. Bull.. 10. No. 2 . Sect. I1 (January 3, 1929). Piroomov and Loomis, Chem. M e t . Eng., 36, 472 (1929). ivilson, I S D E N G CHEM 20, 1363 (192s)
Phosphoric Acid for Determination of Melting Points' Foster Dee Snell 130 C L I N T O X ST.,B R O O K L Y N , P;. \'.
HE usual niethod of determining melting points of organic compounds with a melting point tube attached to a thermometer requires stirring. The Thiele apparatus obviates stirring and has recently been modified ( 1 ) to give more uniform heating. I n the range of 100-300" C. by the use of sirupy phosphoric acid hand stirring can be avoided. This should be applicable also to the Thiele apparatus, although we ha\-e not so applied it. Phosphoric acid, instead of the usual concentrated sulfuric acid, is placed in an open beaker or a double test tube. The sample in the melting point tube is put in place in the usual way and the container is heated. The phosphoric acid begins to lose moisture a t about 100" C. By placing the burner somewhat to one side of the container the steam generated automatically creates a circulation. By proper heating the bubbles of steam do not obscure the view of the 1
Received M a y 17, 1930.
thermometer and melt,ing-point tube and the rate of rise in temperature is uniform. At 213" C. conversion of orthophosphoric acid to pyrophosphoric acid begins, so that the evolution of steam continues up to nearly 300" C. On cooling, if 200" C. has not been exceeded, about 10 per cent of water is stirred in below 100" C. and the apparatus is ready for use again. If heated to 25tk300" C. the liquid tends to gel when cool, but may be dilut'ed with water and on warming will become homogeneous. When containinat'ed with organic matter the acid can be clarified with a crystal of potassium nitrate. One beaker of phosphoric acid mas in use for 6 to 8 determinations a week b y this method for over a year. I n that case an open 150-cc. beaker, with a definite immersion thermometer, was used. Literature Cited (1) Conte, ISD. E s c . C H E M .Anal. , Ed., 2, 200 (1930).
