July 15, 1930 INDUSTRIAL A N D ENGINEERING CHE-XISTRY 287

Per Cent

Figure 3-Finished Chart for Midcontinent Crude

ease with ~vhicli the gas oil would crack and of the knock rating on the resulting ga: -0 1' me.

Paraffin-distillate and lubricating-oil yields are again es- sentially thoqe obtained in pipe-still rather than shell-still equipment. The quality of the lubricating oil obtainable can be closely estimated froni the viscosity-temperature- gravity relationship shown in the work-up chart, the tem- perature being indicative of the flash to be expected. The method, as outlined above, of estimating the viscosity of any par t 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.

weight of accuracv.

The maximum amount of pressable distillate obtainable from a mixed-base crude when operat- ing 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 by doubling the difference between this point and that a t the desired sriscosity. For a paraffin- base crude the cut temperature is usually some- what 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 correspond- ing to the mid-point of the cut is read off the final chart. Then the molecular weight of the paraffin hydrocarbon corresponding to this teni- perature 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

the n-hole calculated from the parts to insure 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 re- quired 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

Y I

Pirooinov and Loomis (.$).

Literature Cited

Calingaert and Davis. ISD. EKG. CHEM., 17, 1287 (192.5). Cox, I b i d . , 15, 592 (1923). Piroornov and Beiswenper. .Im. Petroleum Inst . Bull.. 10. No. 2 . Sect. I1

. I .

(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 CLINTOX 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, al- though 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 pyro- phosphoric 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 de- terminations a week by 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. Esc . CHEM. , Anal. Ed., 2, 200 (1930).