SPECIAL REPORTS AND ESSAYS. I. PHARMACY. ON SPECIFIC VOLUMES.* BY OSCAR OLDBERG, PHARM. D., SAINT LOUIS. The term SPECIFIC VOLUME is proposed by the writer to express in pharmacy and other arts the relative volumes of substances, in the same sense as the term "specific gravity" designates their relative weights. I am aware that the term "specific volume" has been applied of late years in chemical physics to express the relation of the atomic volume to the specific gravity at the ordinary boiling points; but for this purpose the terms "atomic volume," "molecular volume," and "equivalent volume" have also been used, and it is not believed that the use of the term "specific volume" in the sense proposed by the writer will in the least interfere with its limited application in chemical physics. The term specific volume is analogous to, and the parallel of, the term specific gravity, and will be so understood by pharmacists. It is the only term the writer has been able to find which adequately and exactly expresses what is intended, and it was accordingly selected. The specific volumes of substances are inversely as the specific gravities, and parallel with the latter. The volume of one gram of any liquid stated in cubic centimeters expresses its specific volume. Thus, as 1,000 grams of the officinal alcohol measures 1.234.5 cubic centimeters at 25° C. (77°F.), the specific volume of that liquid is 1.2345 at the tempera ture named. As the specific gravity of a liquid or solid is the weight of a certain volume of that liquid or solid divided by the weight of an equal volume of water, so the specific volume of a substance is the quotient obtained by dividing the volume of a certain quantity by weight of that substance by the volume of an equal weight of water. It is, in other words, the quotient obtained by dividing unity by the specific gravity: The product obtained by multiplying the specific gravity by the specific volume is ONE. *Read at the Fourth Session. To illustrate the character and uses of specific volumes, we account for the familiar fact that a pound of alcohol measures more than a pound of water by the fact that the specific volume of alcohol is greater than the specific volume of water. The absolute weight of any given quantity of a liquid, expressed in grams, when multiplied by the specific volume, at once gives the number of cubic centimeters occupied by it. Since the new Pharmacopoeia of the United States was published, the necessity of a table of specific volumes becomes manifest. If we take any one of the pharmacopoeial working formulæ for tinctures, we find that by substituting grams for "parts by weight," the final product is to be one hundred or one thousand grams; but we cannot ascertain how much that product will measure, except by a troublesome division of the number of grams by the specific gravity; whereas, if we know the specific volume, the whole problem then resolves itself into simply multiplying the specific volume by 100 or 1,000, as the case may be. Numerous blunders are being made in attempting to translate the working formulæ of the new Pharmacopoeia from parts by weight into definite quantities by weight and measure, and many of these errors arise from the necessity of comparatively difficult and tedious calculations, in the absence of a table of specific volumes. I have prepared and now present in connection with this paper a table, showing the specific gravities and the specific volumes of the liquids of the Pharmacopoeia, so far as their specific gravities are officially given. It embraces the acids, ammonia, alcohol, diluted alcohol, ether, glycerin, syrup, the solutions, many of the oils, etc. An examination of this table will readily convince any one of the practical usefulness of specific volumes. We find in it, for instance, that the specific volume of ether is 113, that of water is 1, that of glycerin }, that of benzin 12, and that of chloroform 23; therefore 113 pints ether, 1 pint water, pint glycerin, 11⁄2 pints benzin, and 23 pint chloroform, respectively have the same weight. We also learn at once from the specific volume the number of cubic centimeters occupied by each gram of these liquids. The pharmacist can learn by the aid of this table how large a bottle or other vessel it takes to hold a certain quantity by weight of any of these liquids, and that it takes twice as large a bottle to hold a pound of ether as to hold a pound of chloroform. The specific volumes given are of course calculated from the official specific gravities, and to verify their correctness it is only necessary to multiply the numbers by the specific gravities, when the product must in each case be exactly ONE, or as near unity as is practicable. I believe that a table of this kind in our Pharmacopoeia would be of great practical value, as it entirely obviates some of the objections to the method of parts by weight." " The table accompanying this paper shows the weight of 100 fluid ounces, and the volume of 100 avoirdupois ounces, of each of the liquids included in it. TABLE OF SPECIFIC GRAVITIES AND SPECIFIC VOLUMES OF SOME LIQUIDS. 64 Fortior. U. S U. S. (at 15.6° C. U. S. (at 25° C. = 77°) Aqua Destillata 0.812 812. 84.6 1.231 1231. 118.1 928. 96.7 95.8 60° F.). 0.928 0.890 890. 92.7 0.925 VOLUMES. TABLE OF SPECIFIC GRAVITIES AND SPECIFIC VOLUMES OF SOME LIQUIDS. LIQUIDS. WEIGHTS. "It has been said that if snow formed in any month but April be melted and bottled, the water will become ropy; that snow which falls during April, upon the contrary, will furnish water which will remain limpid the summer through, and which can be used by pharmacists and photographExperiments upon this subject are desired." ers. In order to reply to the above query the following course was taken. Snow was collected upon the following dates, viz: November 26, 1882; December 17, 1882; January 1st, February 17th, March 28th, and April 23, 1883. The snow in each case was carefully gathered from an open lot about fifty feet from any building, collected in a clean porcelain vessel, and after Read at the Fifth Session. carefully covering with a napkin, it was placed in a position where the temperature was sufficient to melt it slowly. The resulting water was then filtered through white filter paper into glass-stoppered bottles of the capacity of one pint, which bottles had been carefully cleansed, and the final rinsing being with distilled water; after filling with the snow water, they were set aside in a closet where the average temperature was 78°F. The appearance of the bottles with their contents was observed frequently, yet without disturbing them, until July 15th, when they were carefully compared with each other. To the eye there was no apparent difference, all the samples being limpid, and there was no sign of ropiness in either. The bottles were all well shaken after having first removed the stoppers to allow access of air; they were then returned to the closet and allowed to remain for ten or twele days, when another observation was made, with similar results to the former, except there was a slight sediment in part. Through the kindness of my friend John N. Hurty, M. D., an analytical chemist, who has given the examination of water considerable attention, I am enabled to give the following detailed examination of the foregoing samples of snow waters: .III None. None. None. O .0476 Oxygen absorbed in half hour at 80° Fah. .130 .054 0272 Oxygen absorbed in 12 hours at 80° Fah. .0015 .0787 .157 .228 .275 .0458 Microscopical.-Every sample contained more or less sediment, and flocculent matter, March and December being especially rich, November and April being almost free. With 375 diameters the sediment proved to be a fine white powder, and silicious appearing granules, insoluble in acids. By far the greater proportion of the sediment appeared to the naked eye as brown flocks, but under the microscope proved to be minute filamentous algæ, of a brown-purple color. The plants were composed of cylindrical cells, having attached simple and branched filaments, all being covered with a very delicate gelatinous coat. The total solid matter, which was estimated by evaporating 100 cc., as the table shows was about one-half organic and volatile matter. The or |