the addition of two and the addition of three equivalents of alkali. In this regard they state: "It is found that by specifying ionizations other than those used in the elementary treatment given, we obtain a variety of equations which, upon the assumption of one or several components of small solubility, will reduce to a form giving essentially the same picture as that presented. Thus the equations we have given furnish a correct description of principles but tell nothing whatever of the actual components entering into the problem. This has become evident in our attempts to formulate the very distinct slopes of the experimental curves formed between the addition of two and the addition of three equivalents of alkali." The data given in this paper upon the composition of the aluminium precipitate furnish a qualitative explanation of the results obtained by Theriault and Clark. Further facts are needed, however, in order to attempt a quantitative explanation. The greatest insolubility for an alum solution 0.005 molar with respect to Al, as experimentally determined, occurs between a pH of 6.7 and 7.0 where about 2.75 mols of NaOH per mol Al have been added. On both sides of this, however, ranging from pH of 5.4 to a pH of 8.5, is a broad zone of great insolubility. Theriault and Clark (1923) have found that best and most rapid flocculation of alum solutions occurs at a pH of 5.5. While solutions at this pH are not in the region of greatest insolubility for Al, they are in a region of great insolubility. It is interesting to note that this pH lies at the point where the precipitation of aluminium first approaches completion upon addition of NaOH, and in the region where the greatest proportion of sulphate is found in the precipitate. At this point about 2.4 mols of NaOH per mol Al have been added. In comparing these results with determinations of residual alum found in filter effluents under commerical conditions, a certain amount of variation is observed. Buswell and Edwards (1922) have obtained a curve relating pH and residual alum which suggests that, if data were included for pH values lower than observed, the curve would pass through a minimum at pH 5.5. Baylis (1923) found a minimum of residual alum between a pli of 5.7 and a pH of 6.6. Hatfield (1923) reported a minimum of Al in the filter effluent at pH 6.1. Blum (1916), in his procedure for the analytical determination of aluminium, indicates that complete precipitation takes place between a pH of 6.5 and a pH of 7.5. There seems to be no general agreement as to the particular pH at which aluminium is most insoluble under these varying conditions. In general, however, a relatively broad zone of great insolubility is reported which, broadly speaking, covers about the same ranges of pH values. SUMMARY. 1. A study of the composition of the precipitate formed at different pH values by the addition of sodium hydroxide to alum has been made. 2. Certain precautions to be adopted in the analytical determination of aluminium are stated, and the reasons for these precautions are given. 3. A theoretical and experimental study of the solubility of the aluminium precipitate at different pII values has been made and certain conclusions drawn therefrom. The results obtained are compared to those obtained under varying laboratory and commercial conditions by other workers. BIBLIOGRAPHY. Adolph and Pauli, W. (1921): Physical-chemical analysis of aluminium oxy salts and aluminium oxide sols. Kolloid Z., 29, 281. Bancroft, W. D. (1922): Mordants. II. Alumina. J. Phys. Chem., 26, 501. Baylis, J. M. (1923): The use of acids with alum in water purification and the importance of hydrogen ion concentration. J. Am. Water Works Assoc., 10, 365. Bentley, W. B., and Rose, R. P. (1913): Some colloidal solutions derived from hydrated alumina. J. Am. Chem. Soc., 35, 1490. Blum, W. (1916): The determination of aluminium as oxide. J. Am. Chem. Soc., 38, 1282. Buswell, A. M., and Edwards, G. P. (1922): Some facts about residual alum in filtered waters. Chem. Met. Eng., 26, 826. Clark, W. M. (1922): The determination of hydrogen ions, 2d ed., 48. Denham, H. G. (1908): The electrometric determination of the hydrolysis of salt. J. Chem. Soc., Tr., 93, pt. 1, 42. Grobet, E. (1922): Reaction of sodium hydroxide on aluminium salts. J. chim. phys., 19, 331. Hale, F. E. (1914): The relation between aluminium sulphate and color in mechanical filtration. J. Ind. Eng. Chem., 6, 632. Hatfield, W. D. (1923): Soluble aluminium in filter effluents. Reported at meeting of the American Water Works Association, at Detroit, Mich., May, 1923. Kremann, K., and Hüttinger, K. (1908): Solubility of aluminium hydroxide in solutions of aluminium sulphate and artificial production of alumina. Jahrb. k. k. Reichsanstalt, 58, 637. Kullgren (1904): Om metallsalters hydrolys. Diss. Stockholm. Rose, R. P. (1914): Some reversible hydrosols from aluminium hydroxide. Kolloid Z., 15, 1. Schlumberger, E. (1895): Aluminium compounds. Bull. soc. chim., 3rd. ser., 13, 40. Theriault, E. J., and Clark, W. M. (1923): An experimental study of the relation of hydrogen ion concentrations to the formation of floc in alum solutions. Pub. Health Rpts., 38, 181. (Reprint No. 813.) Williamson, F. S. (1923): Basic aluminuim sulphate. J. Phys. Chem., 27, 284. COLLECTION AND PRESERVATION OF BLOOD SAMPLES FOR DETERMINATION OF CARBON MONOXIDE. By R. R. SAYERS, Surgeon, United States Public Health Service, Chief Surgeon, Bureau of Mines, Department of the Interior; H. R. O'BRIEN, Acting Assistant Surgeon, United States Public Health Service; G. W. JONES, Assistant Gas Chemist, Bureau of Mines, Department of the Interior; and W. P. YANT, Assistant Chemist, Bureau of Mines, Department of the Interior. INTRODUCTION. In investigations relating to poisoning by carbon monoxide it is often desirable to have a reliable method of collecting samples of blood from victims at the place of accident, and of shipping the samples to the laboratory without coagulation. The method should be simple and inexpensive; and it is very important to allow of no change in the amount of carbon monoxide in the samples before analysis, which might result from delays. PLAN OF INVESTIGATION. Two types of containers for blood were investigated, and tests were made to find a suitable preservative which would prevent coagulation. In addition, tests were carried out to determine the gaseous changes taking place in the blood when it was allowed to stand for various periods of time in contact with the preservatives, such as might result in practice during the period between collection and analysis. From these tests suitable types of container and preservative were adapted and are recommended. METHOD OF COLLECTING SAMPLES. The Keidel tube.'-This tube, devised some years ago for taking and shipping of specimens for the Wassermann test, was selected. It is a small, inexpensive article, which is easily handled, collects the sample quickly, and is conveniently shipped by mail. However, the exact design of the tubes on the market was found not to be quite suitable for our purpose, and it was necessary to make the size and type shown in Figure 1. The desired quantity of powdered salt to be used as a preservative and anticoagulant is weighed into a clean, sterile, three-fourths by 5-inch test tube, and the tube is drawn out to a long thin tip. The tube is then evacuated to a pressure of 0.5 millimeters of mercury and sealed off, the total capacity of the finished tube or ampule. being approximately 15 c. c. An ordinary 18 gauge intravenous needle with stylet guard is joined by about 2 inches of medium weight rubber tubing, with small lumen, to the shoulder at the base of the long tip of the ampule. A narrow test tube is placed over the needle. and rubber hose as a cap, and protected from adhering to the rubber 1 A sample bleeding tube for obtaining specimens for the Wassermann Reaction. By A. Keidel. Jour. Am. Med. Assoc., Chicago, Vol. 58, 1912, p. 1579. during sterilization by a thin layer of cotton placed at the point where the tube, ampule, and cap meet. The whole is again sterilized by dry heat at 150° for 30 minutes. Keidel tube method. In collecting the sample, the cap and guard are removed, the person's arm is prepared as for taking a Wassermann sample, and the tip of the needle is inserted in the vein. The rubber tube is then taken gently in both thumbs and forefingers, and the thin neck of the ampule within is broken. When the ampule is full of blood, or has ceased filling, the needle is removed from the arm, the needle with rubber connection is detached, and the ampule is gently rotated for 2 minutes to dissolve the preserving salts. The ampule is then scaled by forcing a small metal cap filled with wax over the broken tip, the cap and wax having been previously sterilized and kept in a small cork-stoppered bottle. By using this cap an effective seal is formed, and any wax that may be forced inside the tube will not aid coagulation. A 15-c. c. tube, or ampule, was used for the investigation described herein, because 15 c. c. of blood was needed for a duplicate analysis by the Van Slyke method used. An 18-gauge needle was found to be most suitable, as it allowed the tube to be filled more quickly, thus decreasing the disturbance to the patient and the probability of coagulation. This larger size also aids the completeness of filling (with a good vein there should be less than one-half c. c. of air left in the tube). Vial method. For use where Keidel tubes might not be available, the suitability of other containers was studied. Two types of 3-dram vials were selected, the one being closed with a plain cork stopper of good grade, and the other with metal screw top lined with a thin cork gasket. The same proportions of preservatives were used, and sterilization was effected as with the Keidel tubes, the only great difference in technique being in the filling of the tubes. This was done by inserting a needle into the vein and catching the blood as it flowed from the end, the blood flowing directly into the vial. When the use of these vials proved satisfactory in 24 instances, other tubes were mailed to the laboratories of the United States Public Health Service hospitals at San Francisco, Calif., Ellis Island, N. J., and Boston, Mass. Through the cooperation of the medical officers in charge at these institutions, the vials were filled and mailed to Pittsburgh, Pa. It was generally found that the screw-capped tubes tended to leak, but with the plain cork stoppers there was no trouble of this kind. In general, the Keidel tubes are preferable, because they fill more quickly; but the plain vials with cork stoppers are excellent sub stitutes. PRESERVATIVES OR ANTICOAGULANTS. Although the prevention of clotting is aided materially by the manner in which the sample is taken, and also by the design of the container, the chief means of preventing coagulation lies in the anticoagulant used. Of these, three were tried, namely, sodium or potassium oxalate, used routinely in blood chemistry to preserve specimens for analysis; sodium citrate, employed in transfusions; and sodium fluoride.3 *Made by melting together 90 parts beeswax and 50 parts Venice turpentine. |