663
V O L U M E 20, NO. 7, J U L Y 1 9 4 8 rachloride, petroleum ether, and acetone are approximately the same as those reoorded in the literature for refined cottonseed oil. On the extraction of the cottonseed with methyl alcohol before the extraction with petroleum ether, one obtains an extract with a saponification number considerably smaller than with the seed that has not been pre-extracted with methyl alcohol. SUMMARY
-4method for the determination of the saponification number of crude cottonseed extracts has been developed. The difficulties with colored cottonseed oil in observing the fading of the red color when the end point of phenolphthalein is reached in the conventional method are eliminated, and the difficulty because of the behavior of gossypol as an indicator has been circumvented by carrying the titrations out in a mixture of isopropyl alcohol and ethylene glvcol with aniline blue as the indicator. The evidence
is that the saponification number of oil obtained from a given qeed specimen is a function of the solvent used in the extraction. LITERATURE CITED
(1)
Boatner, Charlotte, et al., J . Am. Oil Chemists SOC., 24, 376 (1947); Oil & Soap, 21, 10 (1944); J . Am. Chem. Soc., 66, 838 (1944) ; 69,668 (1947).
(2) Frampton, V. L., and Giles, F. K., IBD.Eso. CHEX.,ASAL. ED., 17, 647 (1945). (3) Frampton, V. L., SVebber, H. H., and Giles. F. K., Oil &. Soap, 23, 318 (1946). (4)Palit, S., Ibid., 23, 58 (19461, J . Am. Oil Chemists SOC.,24, 190 (1947); J . Am. Chem. SOC..69,3120 (1947): IND. ENG.CHEV..
ANAL.ED.,18,246 (1946) RhcErvED Kovember 19, 1947. Condensed from a thesis presented by Garland Ned Martin to the graduate faculty of the University of Texas in partial fulfillment of the requirements for the master's degree.
Measurement of Heat of Combustion of Volatile Hydrocarbons Liquid Sample Holder R. L. LETOURNEAU AND ROBERT MATTESON, Caliifornia Research Corporation, Richmond, Calif.
A sample holder, having advantages over existing liquid sample-handling techniques, for holding low boiling liquid fuels in determining the heat of combustion is described. Typical results are given for pure hydrocarbons and production grade motor and aviation fuels. Isopentane is securely held at 25" C., onl? 3" C. below its boiling point.
E
VEX though the petroleum industry's largest volume product is gasoline, there is at present no standard procedure for handling samples of the material in the measurement of its heat of combustion (4). The usual procedure is to use the -4.S.T.11. method for the thermal value of fuel oil ( 8 ) with either of two types of sample holders-gelatin capsules ( 3 ) or glass ampoules (61. The precautions necessary in the successful use of gelatin capsules are involved and lack of attention to any detail leads to erratic results. T w o fundamental difficulties here are a large ratio kCAP SCOTCH CELLULOSE TAPE
of auxiliary material t o fuel sample burned and permeability of the gelatin capsule which requires an evaporation correction during handling. I n addition, the water content of the gelatin must be carefully controlled. The glass ampoule suggested by Prosen and Rossini ( 6 ) is very satisfactory where extreme accuracy is desired, but it is rather difficult to prepare these glass ampoules in routine sork, where the glass blowing is not done by the calorimeter operator. The sample holder described here is a simple corrosion-resistant cup with ordinary cellulose Scotch adhesive tape (Minnesota llining and Manufacturing Company) cover. Others have suggested a similar scheme but have used an inferior covering material for the purpose. For example, Richter (6) described a steel crucible with collodion cap which he claimed is superior to the gelatin capsule; later he used a platinum crucible with the same covering scheme. Considerable difficulty has been experienced by the authors with both collodion and cellophane covers. They are either too brittle or of indeterminate moisture content and they are about as permeable as the gelatin capsule. SAMPLE HOLDER
j - a1-
Figure 1. Sample Holder for Volatile Fuels
The sample holder, shown in Figure 1, is turned from a 2.5-cm. (1-inch) aiameter bar of 52Oj, nickel alloy steel to the dimensions shon-n, which is a convenient size for charging 1ml. of liquid. (This high-nickel alloy is corrosion-resistant but not as good as the illium alloy customarily used for ox gen bombs. The Parr Instrument Company, Moline, Ill., wily furnish this holder in illium.) The capis.turned from a separate piece of the same 52y0 nickel stock to the dimensions shown. The 0.5-inch diameter Scotch cellulose tape circle is conveniently cut with the appropriate cork borer. Procedure for Handling Sample Holder. Before each use the lip oi the sample holder is polished on crocus cloth. The sample holder with cap, but without Scotch tape, is weighed to the nearest 0.1 mg. on a suitable analytical balance. The Scotch tape is placed in the cap of the sample holder and the assembly is again weighed, Kith cap upside down on the balance pan beside the
'
ANALYTICAL CHEMISTRY
664
Table T. Distillation D-86 Start, % J
10 20 30 40 50 60 70 .. 80 90 95
E.P.
Loss
A.P.I. gravity Aniline point,
' F.
Inspections on Fuels
Natiirdl
Rrgular
Premium
91/96
100/130
102 118 124 132 140 150 164 180 198 216 2 52 286 346 2.0 70.1 132.8
98 118 131 153 176 200 223 245 269 297 336 365 402 1.2 59.2 101.1
94 115 126 146 166 188 210 230 250 276 310 344 377 1.2 62.6 108.9
109 135 144 156 166 178 188 198 207 220 237 254 291 1.2 63.9 123.8
118 ~137 147 157 169 181 195 207 217 228 248 271 338 1.2 67.3 139.6
holder. The difference between these t a o weights gives the weight of Scotch tape used to seal the holder. This weight is in the order of 13 mg., which is equivalent to about 2y0of the weight of gasoline. Exactly 1 ml. of fuel is pipetted into the holder with the tip of the pipet on the floor of the cup. The cap with Scotch tape is quickly placed on the cup and pressed into place with a slight twisting motion, and the assembled sample holder is again wei hed to give the weight of sample enclosed. The sample holfer is placed in the Pupporting ring attached to the bomb cap and the previously attached ignition wire is bent so that it lightly tpuches the Scotch tape cap 15-ithouttouching the metal retaining ring. No spiral or coil is necessary, just a simple hairpin bend. Just as the sample holder IS being lonered into the bomb a tiny hole, which may vary in diameter from 0.05 to 0.10 mm., is pricked in the taut cover with a sharp needle. The bomb i.j closed and filled immediately but slowly with oxygen to a pressure of 35 atmospheres. Calorimeter and other Accessories. I n the tests described the Parr Model DD-11 adlabatic oxygen bomb calorimeter was used Rith a single-valve, illium bomb with self-sealing head. Solidstem mercurial thermometers furnished wlth the calorimeter, graduated in units of 0.05' F., were used together with their calibrations. Although temperatures may be estimated to 0.005' F. with the aid of a telescopic reading lens, reproducibillty in readings is not better than 0 . 0 1 O F. and this is the limiting factor, in accuracy so far attainable by this procedure. (Later work using a platinum resistance thermometer showed very satisfactory reproducibility.) The bomb used in these tests had a volume of approximately 360 ml. Iron firing wire supplied by the Parr Instrument Company was used. The lvater equivalent, evaluated n1th approximately 1-gram pellets of benzoic acid undrr the same conditions of test as with the liquid fuel samplpq, mas 2450 gramI., Derdsche Lujtzcissen, 6 , 1 2 8 (April 1939). RECEIVED August 19, 1947. Presented before the Division of Petroleum Chemistry a t the 112th RIeeting of the . 4 v ~ ~ r cCHEMICAL as SOCIETY, New York, N. Y.
