Authors
Lewis Michael SimmonsMartin J. Canny
Topics
Chemical Thermodynamics and Molecular Structurethermodynamics and calorimetric analysesChemical and Physical Properties in Aqueous SolutionsDETERMINATION OF THE BOILING POINTS OF AQUEOUS NITRIC ACID. By L. M. SIMMONS, B.Sc., Ph.D., F.A.C.I., A.R.I.C., and MARTIN J. CANNY.* With two text-figures and three tables. Manuscript received, October 5, 1949. Read, December 7, 1949.| | Inconsistencies | in the published | boiling points of aqueous hydrogen chloride || --- | --- | --- | --- || solutions | led to | the design of a static | method for rapidly determining the boiling || points | of pure | and mixed liquids which | do not attack mercury, glass or tap || lubricant | (Simmons, | 1945). The method | was later developed to eliminate the || tap | lubricant | (Simmons, 1947), and | the present further adaptation described || herein | enables | the method to be used | with liquids which attack mercury, such || as | aqueous nitric | acid. | || | As was the | case for aqueous hydrogen | chloride solutions, the boiling points || of | aqueous nitric | acid have hitherto | been determined by dynamic methods, || and | these are | known to suffer from | two important sources of error, viz. super || heating | and change | in concentration | during the distillation of all samples except || the | azeotropic | solution. The boiling | points of aqueous nitric acid given in the || International | Critical | Tables are based | on the observations of Creighton and || Githens | (1915) | using a dynamic method | due to Young (1902). Although Young || claimed | that with | the large quantity | of liquid present and the small flame that || is | required, there | is no fear of the | vapour being superheated, he later stated in || his | monograph | (1922) that ‘‘ the boiling | point of a liquid can only be correctly || determined | by | observing the temperature | of the liquid itself under such con || ditions | that ebullition | is impossible’. | This latter view is in accord with the || conclusion | arrived | at by Swietoslawski | (1945). || | Table I shows | the values published | at various times for the boiling point || and | composition | of the constant boiling | mixture of water and nitric acid at or || near | standard | pressure. | || | Date. | Observed | by. (Millimetres | | | B.p. | HNO, by | Remarks. | || --- | --- | --- | --- | --- | --- | --- | --- | --- | --- || | | | Mercury.) | | | (° C.) | Weight. | | || | Before | Dalton | et al. Not | | | 120 | 66-70 Reported | by Roscoe, | || | 1861 | | stated | | | | 1861. | | || | 1861 | Roscoe. | 735 | | | 120-5 | 68-0 | | || | 1915 | Creighton | and 760 | | | 121-7- | 68-18— | | || | | Githens. | 121-8 | | | | 69-24 | | || | 1928 | — | 760 121-9 | | | 67-3 | International | Critical | |TABLE I. Boiling Point and Composition of Constant Boiling Aqueous Nitric Acid. Pressure. Percentage Tables. 1949 Simmons’ and 760+0:5 120-6+0-2 | 67-5+0-5 | Present investigation. Canny. * Present address: St. John’s College, Cambridge, England.DETERMINATION OF BOILING POINTS OF AQUEOUS NITRIC ACID. 239 RESULTS. The boiling points found for aqueous nitric acid solutions at 760 mm. by the present method are shown by curve A (Fig. 1). That portion of curve A which represents solutions containing more than 78 per cent. by weight of HNO, is dotted in order to indicate that decompositionBoiling Pontof 760mm. 1 °C0 20 40 60 80 100 7) HNO; by weight. PIGFig. 1.—The Boiling Points of Aqueous Nitric Acid.A. According to the present investigation, observations plottedthus: xX.B. According to the International Critical Tables. Tabulatedvalues plotted thus: A.Creighton and Githens’ observations plotted thus: ©.240 SIMMONS AND CANNY.takes place before the normal boiling points are reached. In such circumstancesa normal boiling point cannot strictly be quoted, for the apparent boiling pointwould be affected by the rate of heating, the presence of light and of catalysts,and by other factors which may affect the rate of decomposition.The data from which curve A was plotted is given in Table II.TABLE II.The Boiling Points of Aqueous Nitric Acid Containing Various Percentages by Weight of HNO,at a Pressure of 760 mm.Percentage Percentage PercentageHNO; by .p HNO, by B.p. HNO, by .p.Weight. (2€:) Weight. (° C.) Weight. (ee! 5 a| 0-0 100-0 | 37-9 110-5 69-2 | 120-4 || --- | --- | --- || 6-1 100-6 | 41-0 111-7 TLL. | 120-0 || 12-9 102-1 | 43-0 112-5 72-2 | 119-7 || 17-0 103-3 | 47-3 114-1 73:7 | 118-9 || 20-3 104-2 | 49-7 115-2 75:3 | 117-6 || 23°3 105-2 | 52-0 116-0 77-4 | 114-4d. || 24-0 105-6 | 53°6 117-0 82-1 | 110-1d. || 27-2 106°6 | 56-0 117-7 85-6 | 106-6 d. || 31-0 107-9 | 58-5 118-9 89-6 | 101-5d. || 32-7 NOSea7 | 62-0 119-6 | || 34°5 109-2 | 67-5 120-6 | |0-0 100-0 37-9 110-5 69-2 120-4 6-1 100-6 41-0 111-7 TLL. 120-0 12-9 102-1 43-0 112-5 72-2 119-7 17-0 103-3 47-3 114-1 73:7 118-9 20-3 104-2 49-7 115-2 75:3 117-6 23°3 105-2 52-0 116-0 77-4 114-4d. 24-0 105-6 53°6 117-0 82-1 110-1d. 27-2 106°6 56-0 117-7 85-6 106-6 d. 31-0 107-9 58-5 118-9 89-6 101-5d. 32-7 NOSea7 62-0 119-6 34°5 109-2 67-5 120-6 d means that the sample decomposed at its boiling point. For the purpose of comparison, Fig. 1 also shows a curve B, drawn according to the data given in the International Critical Tables. On this curve points marked / indicate the International Critical Tables data, while points marked © show the observations listed by Creighton and Githens. It will be seen that the boiling point of the constant boiling mixture is listed by the International Critical Tables as more than a centigrade degree higher than that found by the present method. It is of interest to recall that the same tables quote a maximum boiling point for hydrochloric acid more than a centigrade degree higher than that found by Simmons (1945) in confirmation of the measurements made by Bonner and Wallace (1930). Table III is therefore submitted to replace that given on page 309 of Volume 3 of the First Edition of the International Critical Tables. Tas Le III. B=HNO,.p (°C Moo 760 mm 100-0 ) 106-9 10 113-9 20 119-2 30 120-6 37-2 118-7 45 ih boe3 55 105-2 65 102-2 70The last three entries in Table III refer to temperatures at which decom position accompanies boiling. |DETERMINATION OF BOILING POINTS OF AQUEOUS NITRIC ACID. 241 APPARATUS AND PROCEDURE. The J-tube shown in Fig. 2 is made of soda-glass and has an internal bore of about 7 mm. The length of the longer limb is about 20 cm.; that of theQsx a:2<=S4H & | |Fig. 2.—Boiling Point Apparatus, lapJo BlowerATER UG a shorter, including the stopper P, is about 14 cm. The stopper P is ground to a good fit in the socket at the top of the shorter limb and is surrounded by a cup| | The heating | bath consists of a large beaker containing paraffin B.P. or other || --- | --- | --- || high | boiling | transparent liquid. The beaker is well lagged except for the top || and | for an | observation window in the side. In the beaker is supported a glass || plate | which | touches the sides but whose upper and lower edges are about 2 cm. || respectively | | below the liquid surface and above the bottom of the beaker. The || motor-driven | | propeller causes the liquid to circulate rapidly as indicated by the || arrows | in Fig. | 2 || | The clean | and dry J-tube, without the stopper, was clamped upright and || --- | --- | --- || into | the shorter | limb was poured enough, of the nitric acid solution to reach a || little | more than | half way up the millimetre scales. The tube was then placed || in | the heating | bath so that the bath liquid reached about half-way up the side || of | the liquid | seal cup when the propeller was in motion. The temperature of || the | bath was | then rapidly raised by closing 8, and 8S, until it was about 3° C. || below | the expected | boiling point of the nitric acid solution. S, was then opened || and | closed judiciously | until the solution had boiled gently for a few seconds in || order | to out-gas | it. The J-tube was then removed from the bath and switches || S, | and S, were | opened. || | The rubber tube from the Winchester | air bottle was then slipped over the || --- | --- | --- || open | end of the longer limb and slight | air pressure was applied by manipulating || the | tap until the solution in the J-tube | rose to partly fill the liquid seal cup; the || meniscus | in the longer limb was then | near the bend in the tube. The stopper P || was | inserted in its socket and held | in place by the spring ties. That portion of || the | solution which was trapped in the | cup provided a liquid seal. |242 SIMMONS AND CANNY. to retain a liquid seal. The stopper is held in place by spring ties. Both limbs are graduated in mm. from a datum line perpendicular to the axes of the limbs near the bend to a similar line just below the socket. The heating bath consists of a large beaker containing paraffin B.P. or other high boiling transparent liquid. The beaker is well lagged except for the top and for an observation window in the side. In the beaker is supported a glass plate which touches the sides but whose upper and lower edges are about 2 cm. respectively below the liquid surface and above the bottom of the beaker. The motor-driven propeller causes the liquid to circulate rapidly as indicated by the arrows in Fig. 2 The heater has a resistance of about 80 ohms. Switches 8,, S, and S8,, and the variable resistors R, and R,, enable the temperature of the bath to be raised or lowered rapidly or slowly at will. The clean and dry J-tube, without the stopper, was clamped upright and into the shorter limb was poured enough, of the nitric acid solution to reach a little more than half way up the millimetre scales. The tube was then placed in the heating bath so that the bath liquid reached about half-way up the side of the liquid seal cup when the propeller was in motion. The temperature of the bath was then rapidly raised by closing 8, and 8S, until it was about 3° C. below the expected boiling point of the nitric acid solution. S, was then opened and closed judiciously until the solution had boiled gently for a few seconds in order to out-gas it. The J-tube was then removed from the bath and switches S, and S, were opened. By this time the temperature of the bath had fallen well below the boiling point of the solution, and the J-tube was replaced in the bath, a plumb-line being used to ensure verticality of the limbs. Switches S, and 8, were closed, and R, was adjusted so that the bath temperature rose about 1° C. per minute; R, was found to be about 170 ohms. The barometer was then read and corrected for temperature and gravity. Using this corrected reading, the pressure in the Winchester air bottle was adjusted by manipulating the tap until the mercury manometer indicated that the total pressure in the bottle was 760--0:5 mm. A short-stem thermometer, graduated in fifths of centigrade degrees, was clamped in the bath near the closed limb so that the graduation representing the expected boiling point was visible beneath the surface of the bath liquid through the inspection window. As the temperature neared the boiling point of the solution, a vapour bubble formed beneath the stopper, and the solution was depressed in the shorter and raised in the longer limb. S, was then opened and R, adjusted so that the temperature fell about 4° C. per minute; R, was then found to be about 50 ohms. By opening and closing S, the temperature was adjusted until the menisci in the two limbs were at the same level. A final adjustment of the pressure in the bottle was made to ensure that it was 760 mm., and, if necessary, the bath temperature was altered slightly to compensate for this change in pressure. When the pressure in the bottle was within } mm. of 760 mm., and the levels of the solution in the two limbs differed by not more than 2 mm., the thermometer was read to the nearest 0-:1°C. By manipulating 8S, the temperature was| | As the temperature neared the boiling point of the solution, a vapour bubble || --- | --- || formed | beneath the stopper, and the solution was depressed in the shorter and || raised | in the longer limb. S, was then opened and R, adjusted so that the || temperature | fell about 4° C. per minute; R, was then found to be about 50 || ohms. | By opening and closing S, the temperature was adjusted until the menisci || in | the two limbs were at the same level. A final adjustment of the pressure in || the | bottle was made to ensure that it was 760 mm., and, if necessary, the bath || temperature | was altered slightly to compensate for this change in pressure. || When | the pressure in the bottle was within } mm. of 760 mm., and the levels || of | the solution in the two limbs differed by not more than 2 mm., the thermometer || was | read to the nearest 0-:1°C. By manipulating 8S, the temperature was || maintained | | nearly constant for | five minutes, after which the pressure and || --- | --- | --- | --- || temperature | | were again adjusted as | above, and the temperature was again read. || The | J-tube | was then removed from | the bath, the rubber tube removed from the || longer | | limb, and when the tube | had cooled to ambient temperature, the solution || was | examined | to see whether any | uncondensed bubbles persisted beneath the || stopper. | | | || | It | was found that solutions | containing more than 78 per cent. by weight || of | HNO, | decomposed and turned | brown on heating as described above. The || decomposition | | progressed while the | temperature was maintained at a constant || value, | | so that in order to keep the | menisci of these solutions at the same level, || it | was | necessary to increase the | pressure in the air bottle. When the J-tube was || subsequently | | cooled to room temperature, | a large bubble of gas remained uncon || densed | | beneath the stopper. The | lowest concentration at which this decom || position | | was detected was at 77:49 | HNO, by weight, and the decomposition || became | | increasingly apparent at | higher concentrations. || than of | 70-2 per cent. HNO, by weight were prepared by mixing weighed quantities ‘‘ Analar ’’ concentrated nitric acid and distilled water. More concentrated || --- | --- || | || solutions | were prepared by mixing the ‘‘ Analar”’ acid with a 98-5 per cent. || nitric | acid prepared as follows. Equal volumes of ‘‘ Analar’’ concentrated nitric acid and concentrated || sulphuric in | acid were mixed and distilled at a pressure of about 10 cm. of mercury an all-glass still. The resulting distillate was mixed with an equal volume of || concentrated | sulphuric acid and again distilled at about 10 cm. Hg. The azeotropic solution was prepared by mixing weighed quantities of || ‘* distilled fact assured | Analar ’’ acid and water to yield a 68 per cent. solution of HNO,, and this was. at 760 mm. The first four-fifths of the distillate was rejected. The that the remainder of the distillate was truly the azeotropic mixture was by comparing its boiling point with the boiling points of mixtures of it |DETERMINATION OF BOILING POINTS OF AQUEOUS NITRIC ACID. 243 maintained nearly constant for five minutes, after which the pressure and temperature were again adjusted as above, and the temperature was again read. The J-tube was then removed from the bath, the rubber tube removed from the longer limb, and when the tube had cooled to ambient temperature, the solution was examined to see whether any uncondensed bubbles persisted beneath the stopper. It was found that solutions containing more than 78 per cent. by weight of HNO, decomposed and turned brown on heating as described above. The decomposition progressed while the temperature was maintained at a constant value, so that in order to keep the menisci of these solutions at the same level, it was necessary to increase the pressure in the air bottle. When the J-tube was subsequently cooled to room temperature, a large bubble of gas remained uncon densed beneath the stopper. The lowest concentration at which this decom position was detected was at 77:49 HNO, by weight, and the decomposition became increasingly apparent at higher concentrations. Standardization of the Thermometer. The thermometer was tested by the Standards Laboratory, Sydney, over the range 90°C. to 130°C. for total immersion to an accuracy of +-0-2° C., and the reported corrections were applied to the readings. Preparation of Aqueous Solutions of Nitric Acid. Solutions containing less. with small quantities of concentrated acid and water respectively. The concentrations of all solutions were determined by titration against sodium carbonate solution, using screened methyl orange indicator. SUMMARY. A method has been devised for the rapid determination of the boiling points of pure liquids and liquid mixtures which do not attack glass. The method obviates recourse to calculated corrections for emergent column and variations in atmospheric pressure, requires about 5 ml. of liquid, prevents sensible varia tions in composition of the liquid phase and avoids superheating. The method has been used to correct the list of boiling points of aqueous nitric acid appearing in the International Critical Tables. Solutions containing more than 78 per cent. HNO, by weight are found to decompose at or before reaching their boiling points. The constant boiling solution of nitric acid in water at 760 mm. is found to contain 67-5-+-0-5 per cent. by weight HNO, and to have a boiling point of 120-:6-+0-2°C. at 760 mm. REFERENCES. Bonner, W. D., and Wallace, R. E., 1930. J. Am. Chem. Soc., 52, 1747. Creighton, H. J. M., and Githens, F. H., 1915. J. Franklin Inst., 179, 161. National Research Council of the U.S.A., 1928. International Critical Tables, 3, 309. McGraw-. Hill, New York.| | A method has been | devised for the rapid determination of the boiling points || --- | --- | --- || of | pure liquids and | liquid mixtures which do not attack glass. The method || obviates | recourse to | calculated corrections for emergent column and variations || in | atmospheric pressure, | requires about 5 ml. of liquid, prevents sensible varia || tions | in composition | of the liquid phase and avoids superheating. The method || has | been used to correct | the list of boiling points of aqueous nitric acid appearing || in | the International Critical | Tables. Solutions containing more than 78 per cent. || HNO, | by weight are | found to decompose at or before reaching their boiling || points. | The constant | boiling solution of nitric acid in water at 760 mm. is || found | to contain 67-5-+-0-5 | per cent. by weight HNO, and to have a boiling || point | of 120-:6-+0-2°C. | at 760 mm. |244 SIMMONS AND CANNY. Roscoe, H. E., 1861. Quart. J. chem. Soc. Lond., 13, 146. Simmons, L. M., 1945. Tuis JourRNAL, 79, 48. 1947. Aust. chem. Inst. J. and Proc., 14, 51. Swietoslawski, W., 1945. Ebulliometric Measurements, p. 2. Reinhold Publishing Corporation, New York. Young, S., 1902. J. chem. Soc., 81, 772. —-————— 1922. Distillation Principles and Processes, p. 22. Macmillan, London. The Scots College, Sydney. The Glasgow Academy, Glasgow, Scotland.Simmons, Lewis Michael and Canny, Martin J. 1950. "Determination of the boiling points of aqueous nitric acid." Journal and proceedings of the Royal Society of New South Wales 83(4), 238–244. https://doi.org/10.5962/p.360563.View This Item Online: https://www.biodiversitylibrary.org/item/173872DOI: https://doi.org/10.5962/p.360563Permalink: https://www.biodiversitylibrary.org/partpdf/360563Holding Institution Smithsonian Libraries and ArchivesSponsored by Biodiversity Heritage LibraryCopyright & ReuseCopyright Status: In Copyright. Digitized with the permission of the rights holderRights Holder: Royal Society of New South WalesLicense: http://creativecommons.org/licenses/by-nc-sa/3.0/Rights: https://www.biodiversitylibrary.org/permissions/This document was created from content at the Biodiversity Heritage Library, the world's largest open access digital library for biodiversity literature and archives. Visit BHL at https://www.biodiversitylibrary.org.This file was generated 31 March 2024 at 06:13 UTC
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PublishedDec 6, 1950
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