In a recent article, Sollmann[172] presented various suggestions for the compounding of paraffin films. Some of the formulas were promising and others were not, but all were simple. He did not try to imitate “Ambrine.” Lieut.-Col. A. J. Hull[173] of the Royal Army Medical Corps, after experimenting with different combinations, concluded that a mixture of “1 part resorcin, 2 parts eucalyptus oil, 5 parts olive oil, 25 parts soft paraffin [petrolatum][174] and 67 parts hard paraffin” served the purpose as well as “Ambrine.” The following formula, which might be called Asphalt-Paraffin No. 21, much more closely resembles “Ambrine,” and it seems to have certain advantages, due to the use of a more suitable grade of paraffin:
Paraffin[175] (M. P. by U. S. P. method 47.2 C.) | 97.5 | gm. | |
Asphalt | from 3 | to 5 drops | |
Olive oil | 1.5 | c.c. | |
Photographic reproduction from a booklet on “Thermozine” showing that it is identical with “Ambrine.”
About 10 c.c. of “asphalt varnish” (B. Asphaltum)[176] is placed in a beaker and heated on the steam bath for one-half hour. From 3 to 5 drops, delivered from a 1 c.c. pipet, are then placed in a casserole, and 1.5 c.c. of olive oil added. The mixture is heated and stirred for a few minutes until perfect solution is effected. To this is then added, with stirring, the paraffin, which has been previously melted. When it is cooled, a brown solid is obtained.[177] The physical factors of this paraffin mixture are, melting point 45.4 C. (U. S. P. method); plasticity, 28.5; ductility, 29; it is very pliable and strong at 38 C., and adheres exceedingly well to the skin, although it detaches easily. This mixture, which is easy to prepare, is inexpensive, the cost of the materials being approximately 10 cents a pound.
Both Hull and Sollmann noticed that tarlike substances and melted paraffin do not mix well. This is noticeable in “Ambrine,” which cannot be called an “elegant” preparation. The difficulty may be overcome by first mixing hot olive oil and asphalt; the asphalt will then go into solution. It is interesting to note that the suggested formula (as well as others which were also prepared) is not as plastic as the paraffin itself.[178] This is also true of “Ambrine.” On the other hand, the melting point of the paraffin is higher. The important point, however, in compounding all paraffin preparations, is to select a proper grade of paraffin as elaborated below.
EXAMINATION OF PARAFFINS AND PARAFFIN PREPARATIONS
Photographic reproduction (greatly reduced) of a full page magazine advertisement of “Thermozine,” the name under which “Ambrine” was sold to the public.
The name “paraffin” generally applies to a colorless and tasteless waxlike substance that is solid at ordinary temperature. It is composed of saturated hydrocarbons, that is, they are unable to take up any more hydrogen, and thereby are quite stable; the hydrocarbons in paraffin have the general formula of CnH2n+2, ranging as high as C24H50 to C27H56. Paraffin may be found in crude form in coal, from which source the first paraffin candles were made. It may be produced from the distillation of brown coal, as in Germany, or from bituminous shale. In America, it is obtained chiefly from the distillation of crude petroleum, being in the residue after the distillation of such products as naphtha (gasoline), kerosene and the lubricating oils. The residue is treated by one of a number of processes causing the unpurified solid paraffin to be made available. The crude paraffin is either sold as such, or is refined. Paraffin or “paraffin waxes”[179] are designated in the trade by their melting points (which in the “American standard” is expressed in Fahrenheit degrees), and as to their state of refinement as “crude,” “semirefined” and “fully refined” paraffin. There are certain chemical and physical differences so that two refined waxes having the same melting point would not have the same plasticity. The higher melting point varieties of paraffin are hard and tough at room temperature: when melted, paraffin expands and forms a thin mobile liquid.