amine were tested for interference in the oxime determination. None of these compounds produced color. Separate Determinations of Oximes and Hydroxylamine. Although the p-nitrobenzaldehyde method, as described, will not distinguish between oximes and unsubstituted hydroxylamine, a modified procedure probably could be provided for that purpose. For example, tests indicated that under proper conditions, hydroxylamine can be oxidized with iodine, leaving the oximes essentially unchanged. Tests also indicated that free hydroxylamine can be determined independently in the presence of oximes by close control of the pH and other reaction conditions. Optimum conditions for these adaptations have not yet been established; but as time permits, work will be done to provide information. Hydroxamic Acids and Amidoximes. In mineral acid media, hydroxamic acids are hydrolyzed to hydroxylamine and the parent carboxylic acid. Therefore, under proper conditions, the p-nitrobenzaldehyde method should be adaptable to the determination of hydroxamic acids. In the present method, however, these compounds do not hydrolyze completely, making a correction for their interference in the oxime
analysis difficult. There is evidence that by using perchloric acid as the catalyst and by applying other more rigorous reaction conditions, complete hydrolysis of hydroxamic acids can be achieved. Also, limited work has indicated that some oximes can be determined directly in the presence of hydroxamic acids simply by substituting formic acid for hydrochloric acid as the catalyst. Under these conditions, hydrolysis of hydroxamic acids is negligible. Based on this observation, it is possible that the use of formic or other weak acids can also provide some degree of specificity between oximes of high and low reactivity. Although amidoximes reportedly are hydrolyzed readily in neutral solutions to form hydroxylamine and the parent amides, they form stable salts with acids and, therefore, do not interfere in the determination of oximes by the present method. Tests showed that neither acetamidoxime nor nicotinamidoxime at relatively high concentrations had any adverse effect on the determination of acetone oxime. RECEIVED for review October 4, 1967. Accepted December 13,1967.
Determination of Minute Quantities of Water in Gas or Liquid by Cobaltous Chloride Indicator Taiichi Asamil Department of Chemistry, 406th Medical General Laboratory, APO 343, San Francisco, Calif,
A UNITEDSTATESAir Force airplane flying at a height of approximately 15,000 feet suddenly went out of control and crashed. Investigation of the accident suggested that a small amount of water in the pilot’s breathing oxygen froze shut the supply nozzle, cutting off his oxygen, and ultimately causing him to lose consciousness. This laboratory was requested to examine the moisture content of the batch of oxygen involved in this accident. A method was developed whereby equipment and chemicals found in an ordinary chemical laboratory can be used for such an examination without expensive electronic equipment, such as an electronic dew-point hygrometer, or unstable reagents, as in the Karl Fischer method ( I ) . The fact that the color intensity of cobaltous chloride and the presence of moisture are inversely proportional is the basis of this quantitative procedure. Although the qualitative use of cobaltous chloride is common, its application in a quantitative analysis, such as the presented method to determine a minute quantity of water in gas or liquid, is new. PAPER INDICATOR
Materials and Equipment. DRIEDETHER. Diethyl ether, purified and free of peroxides, is dried by mixing with anhydrous sulfate and filtering. It is stored in a cool place in bottles which contain anhydrous sodium sulfate wrapped in filter paper. Present address, 3-3, Daita-4, Setagaya-ku,Tokyo, Japan. (1) Karl Fischer, Angew. Chem., 26, 394 (1935).
648
ANALYTICAL CHEMISTRY
PAPERINDICATOR.Cobaltous chloride indicator is prepared by dipping filter paper into a 3Z water solution of cobaltous chloride. The paper is allowed to dry by hanging in air. The lower edge, about 1 cm, is cut off leaving paper with a uniform distribution of the chemical. This filter paper is cut into 2- X 14-cm strips and stored in an air-tight container with anhydrous calcium chloride as desiccant. STANDARD ETHER-WATER SOLUTIONS.Aliquots of a stock solution of 50 mg of water in 100 ml of dry ether are diluted quantitatively with absolute ether to give standard solutions containing 0.5, 1, 2, 5, and 10 mg of water per 100 ml of ether. Standards should be prepared immediately prior to use. FRIITED-GLASS DISKBUBBLE BOTTLES. These bottles, 200 ml in size, are used to hold the standards and anhydrous ether for the determination. Procedure. Six bubblers are used, five for standards, and one containing the dry ether for the unknown. A strip of paper indicator is added to each bubbler with a stopper, and oxygen is bubbled through the bubbler containing the dry ether at a rate of 1 liter per minute for 10 minutes. The bubblers are allowed to stand for 15 minutes with occasional shaking. The color of the paper in the unknown is then visually compared with the color of the papers in the standards to determine the grams per m3water content. Table I shows the results of this procedure for four samples of Japanese medical oxygen and four samples of U. S. Army aviation oxygen and indicates high water content (1-2 grams per m3) for U. S. Army Tag No. 6. Discussion. The most effective concentration of cobaltous chloride to use to prepare the indicator was determined by evaluating solutions of 20, 5.0, 3.0, and 2.0%. Results indicated that a 3% solution for water concentration of 1 to 10 mg per 100 ml of ether-water standard was optimum.
Table I. Water Content of Oxygen by Paper Indicator Sample No. Japanese Medical O2No. 1 Japanese Medical O2No. 2 Japanese Medical O2No. 3 Japanese Medical O2No. 4 U. S. Army Tag No. 1 U. S . Army Tag No. 6 U. S. Army Tag No. 9 U. S . Army Tag No. 10
Purity of 02, 99.6 99.6 99.6 99.6 99.7 98.9 99.3
99.25
Water content, g/m3 0.1-0.5 0.2 0.2
0.2 0.2
1.5 0.5 0.8
Table 11. Water Content of Oxygen by Gravimetric Method with PP05 Water Sample No. Purity of 02, content, g/m3 Japanese Med. O2No. 1 99.6 0.42 Japanese Med. O2 No. 2 99.6 0.25 Japanese Med. O2No. 3 99.6 0.50 U. S . Army Tag No. 6 98.9 2.03 U. S. Army Tag No. 9 99.3 0.45
Distance (mm)
Figure 1. Calibration curves for the detector Primary calibration curve of detector. Humidity, 100% at 30" C; 30.89 g/m3 = 30.39 mg/l. Rate of pushing, 50 m1/30 sec; 50 m1/60 sec for final 50 ml 0 Final calibration curve for the detector
The time required to allow the gas to pass through the dry ether depends on the color change of the indicator-a light blue being more effective than a faded weakened color. Proper lighting is important in comparing the paper indicators. A diffused strong light from behind the viewer gives good results. Rotating the bubbler bottle to avoid interference from the curved glass surface is helpful. This method can be used to determine water content in poorly hydrophilic organic solvents, such as petroleum products, ketones, absolute higher alcohols, etc. Table I1 compares the results with this method and those of the traditional gravimetric method (2) on two of the samples in Table I. This new method is simpler and just as precise as the traditional method, gives results much faster, and is reliable. There is no danger of contamination from atmospheric humidity unless there is unnecessary exposure of the container to air. SILICA GEL DETECTOR
Silica gel treated with cobaltous chloride can also be used to make an effective detector for water in gaseous substances. When water is absorbed in such a detector, the blue color of the dried form is converted to faint pink. When the detector is a column of treated silica gel in a capillary tube, the humid gas can be passed through the system at such a rate that an easily detected sharp border line is formed between the faint pink and the blue silica gel. The border line demarks the boundary between the silica gel that has not reacted with water vapor and that which has completed this reaction. The distance that this border moves when a gas sample is forced through the column is a measure of the amount of (2) Wilfred W. Scott, "Standard Methods of Chemical Analysis,' Van Nostrand Co., New York, 1925, p 2408.
water present. It should also be noted that the sharpness of the boundary is influenced by the particle size of the silica gel. Materials and Equipment. COBALTOUS CHLORIDE.For oxygen analysis, a ZOZ solution was used. SILICAGEL. Silica gel, 40-60 mesh, was boiled with HCl and then with concentrated HN03. It was washed with distilled water, dried by filtering through a Buchner funnel, and allowing to stand in air overnight. GLASSTUBING. Capillary glass tubing, 17 cm in length, and 4 mm in diameter was used. HANDPUMP. A hand pump, capacity 50 ml, was prepared for use with common detector tubes (Komyo Rikagaku Kogyo Co., Ltd., Tokyo). HUMIDITY CHAMBER.A humidity chamber, 10 m3, with a wooden tube containing 0.5 m 3water equipped with a heater, was used. An ideal chamber is a Japanese bathroom with a bath tub, in which a humidity of 91% can be steadily maintained by adjusting the flame of the burner. Water-saturated air, 100% humidity, can easily be maintained by application of a small jet sprayer in the room at 30" C. An American bath tub can also be used for this purpose, if a small amount of hot water is allowed to run constantly. PREPARATION OF DETECTOR TUBE. Silica gel is impregnated with cobaltous chloride by allowing it to soak in the solution for 1 hour. The mixture is filtered through a Buchner funnel with gentle vacuum and the separated silica gel is dried in an oven at 80" C overnight and stored in a desiccator with calcium chloride. The concentration of the cobaltous chloride solution should be rather low for gases with a low water content; otherwise the length of absorption in the capillary tube will be too short to measure. The capillary glass tube is filled to 10 cm with the treated and dried silica gel. The ends are sealed with cotton plugs and fused. The sealed detectors can be stored safely for long periods of time. CALIBRATION OF DETECTOR TUBE. After cutting off both ends of the detector, the tube is attached to the hand-pump and air is forced through the tube at the rate of 1 ml/sec. Fifty-ml portions of saturated air were passed through the tube and the border lines are marked at successive aliquots. After the first 50 ml a mark is made on the tube and this is considered the 0-base line. The results are shown in Figure 1; the final calibration curve is shown in Figure 1 also. The latter curve is the working curve. The water content of VOL. 40, NO. 3, MARCH 1968
649
of time in which rather low rates of pumping are adopted only at a few points. Comparing the paper indicator with the detector, the latter is rather simple, rapid, and reliable for the determination of water content of a given gas if the water content is relatively high; however, a small fluctuation is unavoidable. The paper indicator method gives more reproducible results, and more accurate values, especially if the method is repeated with newly made standards. The detector method, if used for lower water content samples will give proper results by passing larger amounts of gas, and reducing the final velocity to make the boundary line clear.
saturated air was computed using data from the Handbook of Chemistry (3). Experimental. An oxygen gas sample with 0.5 gram of water per cubic meter (the same value for three runs by the paper indicator method) was analyzed for its water content. The gas was connected to the detector tube and a gas meter. The rate of flow was 100 ml/min at the beginning and 50 ml/ min for the final 1 liter. The results were between 0.45-0.53 gram/m3 for three runs. Discussion. In the calibration of the detector the optimum rate of introducing water-saturated air was found to be 1 ml/sec. If the rate is doubled, the border line between the two phases of moisture absorbed and nonabsorbed was found to be faded and difficult to detect. The border line is sharper with lower rates. The rate of absorption is independent of the rate of introducing moisture into the silica gel within a certain limit. It was noted that the amount of water absorbed is in proportion to the length of the distance of the absorption in the tube. Adopting these principles, a more or less accurate calibration curve can be obtained in a short period
The author is indebted to Komyo Rikagaku Kogyo, Co., Ltd., who generously offered him the necessary materials to carry out the experiment for the water detector.
(3) “Handbook of Chemistry,” Handbook Publishers, U. S. A., 1956,p 1412.
RECEIVED for review April 20, 1967. Accepted December 14, 1967.
ACKNOWLEDGMENT
Determination of Water and Hydrogen Bonding in Tr is-[1- (2- Methyl)Azi ridinyI] Phosphine Oxide by Infrared and Nuclear Magnetic Resonance Spectrometry A. S . Tompa and R . D . Barefoot Nacal Ordnance Research, Naljal Ordnance Station, Indian Head, Md. 20604
THEAPPLICATION of infrared and nuclear magnetic resonance (NMR) techniques to the analysis of HzO-DzO system is well known (1-6). However, the determination of water in organic compounds is complicated by the existence of bonded and free water species which are concentration and temperature dependent, and do not in general obey Beer’s law. In the present study, water may exist in the hydrogen-bonded group in tris-[l-(2state owing to the presence of -P=O methy1)aziridinyll phosphine oxide (MAPO). The spectrometric techniques employed have the advantage of being fast, reproducible, and requiring no sample preparation. In the infrared method, a 0.0932-mm cell was used to scan the 3700 to 3100 cm-l region and the water absorption measured by graphical integration with a planimeter and by the base line method. In the NMR study, the intensity of water absorption was determined by peak integration with a digital voltmeter readout and by peak height measurements. The concentration range investigated was 0.2 to 1.2% water. In addition a concentration and temperature dependent NMR study of hydrogen bonding in H20-MAP0 solution was carried out. (1) J. Gaunt, Spectrochim. Acta, 8, 57 (1956). (2) J. Gaunt, Analyst, 79, 580 (1954). (3) J. Gaunt, J . Appl. Chem. London, 6 , 277 (1956). (4) V. Thornton and L. E. Condon, ANAL.CHEM., 22, 690 (1950). (5) N. R. Trenner, B. H. Arison, and R. W. Walker, Zbid., 28, 530 (1956). (6) A. M. J. Mitchell, and G. Phillips, Brif. J. Appl. Phys., 7, 67 (1956).
650
0
ANALYTICAL CHEMISTRY
EXPERIMENTAL
The infrared spectra were recorded on a Perkin-Elmer Model 421 spectrophotometer. The infrared cell (0.0932 mm) was calibrated before use by the interference fringe method. Infrared area measurements were made with a planimeter (Gelman Instrument Co.). The absorbance values reported are divided by the cell thickness and are in units of absorbance per millimeter. The NMR spectra were recorded with a Varian DA-60-EL spectrometer equipped with a superstabilizer. The integrator output voltage was measured with a Hewlett-Packard 3440A digital voltmeter. Only the peak height of the water absorption was measured with instrument factors held constant. The readings (peak area and peak height) reported are the average of 10 scans. MAPO was obtained from Interchemical Corp. and distilled before use. A series of solutions prepared by direct weighing were used for the calibration study. MAPO is very hygroscopic and it is recommended that solutions be prepared in a dry box. DISCUSSION
MAPO is a widely used crosslinking agent which readily reacts with polymers which contain an active hydrogen. The presence of water in MAPO can cause it to undergo a change in its functionality (7) so that the determination of the amount of water present is necessary. (7) R. A. H. Strecker, and A. S. Tompa, Polymer Preprints, 8, 562 (1967).
