236 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS REFERENCES (1) Butcher, E. O., "The Hair Cycles in the Albino Rat," dnat. Rec., 61, 5 (1934). (2) Butcher, E. O., "The Oxygen Consumption of the Skin During the Hair Cycle in the White Rat," rim. 7. Physiol., 138, 408 (1943). (3) Butcher, E. O., and Grokoest, A. W., "The Influence of Tissue Fluid on Hair Growth," Growth, 5, 175 (1941). (4) Butcher, E. O., "The Effects of Applications of Various Substances on the Epidermis of the Rat," it. Invest. Derrnatol., 16, 85 (1951). (5) Periman, A., "The Effect of Certain Lubricating Agents and Coarse Foods Upon the Cornification of the Oral Mucosa of the White Rat," 7. Dent. Res., 29, 1 (1950). (6) Harry, R. G., "Skin Penetration," Brit. 7. DermatoL & Syphilol., 53, 65 (1941). (7) Eller, J. J., and Wolff, S., "Permeability and Absorption of the Skin," drch. Dermatol. & Syphilol., 40, 900 (1939). (8) Calvery, H. O., Draize, J. H., and Lang, E. P., "The Metabolism and Permeability of Normal Skin," Phys. Reviews, 26, 495 (1946). (9) Butcher, E. O., "The Penetration of Fat and Fatty Acids Into the Skin of the Rat," 7. Invest. Dermatol., 21, 43 (1953). (10) MacKee, G. M., Sulzberger, M. B., Hermann, F., and Baker, R. L., "Histological Stud- ies on Percutaneous Penetration with Special Reference to the Effect of Vehicles," Ibid., 6, 43 (1945). (11) Johnston, G. W., and Lee, C. O., "A Radioactive Method of Testing Absorption from Ointment Bases," 7. rim. Pharm. dssoc., 32, 278 (1943). (12) Butcher, E. O., "Penetration of Radioactive Stearic Acid Into the Skin of the Rat," 7. Invest. DermatoL, 21, 243 (1953). (13) Burch, G. E., and Winsor, T., "Diffusion of Water Through Dead Plantar, Palmar, and Torsal Human Skin and Through the Nails," drch. Dermatol. & Syphilol., 53, 39 (1944). (14) Ralston, A. W., "Fatty Acids and Their Derivatives," New York, John Wiley & Sons, Inc. (1948), p. 78. (15) O'Brien, J.P., "The Effect of Lipoid Solvents on the Pores of the Skin," it. Invest. Der- matol., 15, 141 (1950). THE USE OF THE PENETROMETER IN THE DETERMINATION OF CONSISTENCY OF PETROLEUM JELLY* By R. T. DOBSON Chesebrough Manufacturing Co., Ltd., London, England THE OBJECT of this short talk is to explain to those not familiar with the penetrometer the working method to be employed with this apparatus and precautions which should be undertaken to ensure that repeatable and comparable results may be obtained which are indicative of differences in consistency between petroleum jellies from different sources. As many of you will be aware, the consistency of petroleum jelly can vary sufficiently to cause subtle differences in the finished product in which it is used and, although a Yellow B.P. W/A Grade 45 or a White B.P. W/A Grade 40A or 40B may be specified, you may not always receive supplies derived from * Presented at the April 9, 1954, Meeting, London, England.

USE OF PENETROMETER WITH PETROLEUM JELLY 237 the same source. The B.P. specification for melting point range for both white and yellow jelly lies between 38 and 56øC. and, even though you ob- tain supplies with a melting point with a much smaller range, say 4øC., considerable differences may be felt between samples when handled. Later in this talk, I shall attempt to show you that, although a number of samples of petroleum jelly can have melting points lying within 3øC. of each other, a very considerable difference can exist in the consistency of the samples. In fact, samples having a melting point varying by only 0.2øC. can have a difference in consistency of 2.8 min. At this point, it may be as well to attempt a definition of consistency. Briefly it is the degree of firmness or solidity of the sample and is defined by the penetration of a standard cone into the sample, the depth of penetra- tion being measured in 1/10 ram., this measurement being the numerical value reported. The consistency of a sample of petroleum jelly will vary somewhat, depending on conditions to which the sample has been sub- jected. It is therefore important that samples shall always be subjected to the same set of conditions when being compared for a consistency deter- mination by the penetrometer. The containers for holding the sample to be tested should be cylindrical with a flat bottom and constructed from metal of sufficient gauge to prevent any give at the side of the container when handled. It is preferable for the container to have a well-fitting, slip-on cover. The size specified by the Institute of Petroleum is 2a/16 in. internal diameter X l a/8 or 2•/4 in. in depth (the deeper vessel being used for samples with a consistency of over 225), whereas A.S.T.M. specified 4 4- •/4 in. diameter and 21/2 in. or greater depth. In my opinion, the larger container is to be preferred because of the greater number of tests which can be carried out on the one sample. The coded containers should be heated to 180øF., filled to a level just be- low the top rim with petroleum jelly which has been melted in a constant temperature oven at 180øF., and the filled samples allowed to cool naturally on a level bench free from vibration. The samples should be shielded from direct sunlight or draught and if possible should be in a temperature main- tained at 77 q- 5øF. After the samples have solidified, they should be allowed to age for not less than sixteen hours before testing and during at least six hours of this time the sample should be in air maintained at 77 m IøF., or the lids sealed and the container completely immersed in a water bath maintained at 77 4- IøF. It is preferable that the sample be tested without disturbance of the surface but if it is found, as is sometimes the case, that the surface is depressed toward the centre, the surface may be carefully cut level with a sharp blade, care being taken not to work the surface during this operation. If the surface is badly depressed at the centre, the sample is best discarded. If the cone temperature varies by more than 3 ø from 77øF., its temperature should be adjusted to 77 m 1 øF.,