US3739639A - Semicontinuous dilatometer/calorimeter - Google Patents

Abstract

A semi-continuous dilatometer/calorimeter is formed of a mixing chamber and a stock chamber which are interconnected together. The dilatometer/calorimeter has means to introduce into the mixing chamber a portion of the liquid present in the stock chamber, whereby this portion of liquid is caused to be mixed with the liquid present in the mixing chamber. The apparatus comprises means to determined the liquid volume decrease of the stock chamber and the liquid volume increase in the mixing chamber.

Description

United States Patent 1 Rue] et al.

[ SEMICONTINUOUS DILATOMETER/CALORIMETER [75] Inventors: Maurice Ruel, Sherbrooke, Quebec, Canada; Jean-Marie Janssens, Billancourt, France; Real Broussear, Sherbrooke, Quebec, Canada [73] Assi g nee: Universite De Sherbmdlie: he r brooke, Quebec, Canada [22] Filed: June 14, 1971 [21] Appl. No.: 152,717

[52] US. Cl 73/190 R [51] Int. Cl. G01k 17/00 [58] Field of Search 23/253 R, 259;

[5 6] References Cited UNITED STATES PATENTS 3,477,820 11/1969 Wadso 73/190 3,012,863 12/1961 Feichtmeir 23/253 11 3,739,639 June 19, 1973 5/1965 Rubens et al. 73/16 OTHER PUBLICATIONS Jeener Low Temperature Mixing Calorimeter for Liquids" in Review of Scientific Instruments vol. 28 No. 4 April 1957.

Primary Examiner-Herbert Gold-stein Attorney-Raymond A. Robic [5 7] ABSTRACT A semi-continuous dilatometer/calorimeter is formed ofa mixing chamber and a stock chamber which are interconnected together. The dilatometerlcalorimeter has means to introduce into the mixing chamber a por tion of the liquid present in the stock chamber, whereby this portion of liquid is caused to be mixed with the liquid present in the mixing chamber. The apparatus comprises means to determined the liquid volume decrease of the stock chamber and the liquid volume increase in the mixing chamber.

8 Claims, 6 Drawing Figures manual 1 am:

SKUIBHI INVENT ORS Maurice RUEL Jenn-Marie JANSSENS Real BROUSSEAU ATTORNEY PATENIEU- 3.739.639

SHEEI 2 II 4 O 0 l 1 X1 7 2 INVENTORS Maurice RUEL Jean-Marie JANSSENS Real BROUSSEAU ATTORNEY Pmcmw m 9 V (cm /q mole) SHEEI 3 (I 4 INVENTORS Maurice RUEL Jean-Marie JANSSENS Real BRDUSSEAU ATTORNEY SEMICONTINUOUS DILATOMETER/CALORIMETER This invention relates to a semi-continuous dilatometer/calorimeter. More particularly, the present invention is directed to an apparatus for determining the volume of mixing and the heat of mixing in a semicontinuous fashion.

When forming mixtures of liquids, it often happens that the total volume of the mixture is not the same as the sum of the volumes of each individual component. Similarly, when mixing liquids to form a mixture, there is a possibility of a temperature variation of the resulting mixture with respect to the temperature of each liquid component.

Many types of dilatometer have been proposed for the purpose of measuring volumes of mixing and none to measure heat of mixing ans volume of mixing simultaneously. Some of these apparatuses give satisfactory results, however they all have serious disadvantages. For example, the solutions forming the binary mixtures are often in contact with mercury. It will be realized that mercury and the impurities which are present therein can react with the solutions through complicated chemical reactions and can therefore have some influence on the precision of the results. Another disadvantage is that in most cases, there is a relatively large vapor space in the dilatometers with the consequence that the volatility of the solutions may create errors in the results. Finally, in most cases the dilatometer enables only one data to be taken at the same time. The period of time necessary to perform a plurality of tests is therefore quite long.

In order to overcome the above disadvantages, we have provided a semi-continuous dilatometer/calorimeter which is formed of a mixing chamber and a stock chamber which are interconnected together. The dilatometer/calorimeter has means to introduce into the mixing chamber a portion of the liquid present in the stock chamber, whereby this portion of liquid is caused to be mixed with the liquid present in the mixing chamber. The apparatus comprises means to determine the liquid volume decrease of the stock chamber and the liquid volume increase in the mixing chamber.

In the drawings which illustrate the invention,

FIG; 1 is a longitudinal cross-section view of the dilatometer/calorimeter according to the invention;

FIG. 2 is a curve based on experimental data of the volume of mixing for the system benzene-cyclohexane;

FIG. 3 is a curve based on experimental data of the volume of mixing for the system ethanol-n-heptane;

FIG. 4 is a schematic illustration of the arrangement and electrical connections required for operating the dilatometer illustrated in FIG. 1;

FIG. 5 is a view showing the T-opening of the valve in the open position thereof; and

FIG. 6 is view showing the T-opening of the valve in the closed position.

With particular reference to FIG. 1 of the drawings, it will be seen that the dilatometer/calorimeter l of the present invention is formed with a stock chamber 3 and a mixing chamber 5. The mixing chamber 5 is divided into two portions 7 and 9. In FIG. 1, portion 7 is the right hand portion and portion 9 is the left hand portion. Referring to the drawings, particularly to FIG. 1, it will be seen that the right hand portion 7 is conical as illustrated. The right hand portion 7 of mixing chamher 5 contains the instrumentation required for mea suring and controlling the properties of the solution formed by mixing two liquids. With reference to FIG. 1, it will be seen that the conical portion 7 of the mixing chamber 5 contains a temperature detector 11, a heating element 13 and a magnetic agitator 15. The mag netic agitator 15 is of standard construction well known to one skilled in the art and has only been schematically illustrated in the drawings. It could for instance be covered by a chemically inert material and be operated by a magnetic bar outside the dilatometer. The magnetic bar could be mounted on a flexibel shaft driven by a variable speed motor.

The left hand portion 9 of the mixing chamber 5 is cylindrical, as shown in FIG. 1, in which fits a piston 67 which has been machined with high precision, the purpose of which will be given hereinbelow.

The stock chamber 3 is essentially the same as the mixing chamber 5 except that it includes no measuring instruments and no agitator. In this case, the left hand portion 25 is conical and the right hand portion 27 is cylindrical.

The stock chamber 3 and the mixing chamber 5 are interconnected by means of a small axial passage 29 which, as illustrated, is as short as: possible. Along the axial passage 29 there is a conical valve 31 which is used to open or close the passage 29. The valve can be tightened in its seat 33 by means of a bolt and nut arrangement 35 in order to make sure that the valve has a T opening 36 to allow for expansion in the valve during the preliminary heating or cooling of the solution to bring it to the desired temperature. Another reason for the presence of the T opening is to facilitate the evacuation of air bubbles which could still be imprisoned in the valve when filling the stock and mixing chambers 3 and 5.

Each chamber 3 and 5 is provided with a corresponding capillary tube 37 and 39 which rises above the conical portion of a corresponding chamber. Both capillary tubes are identical and are mounted exactly in the same manner over the conical portions of both chambers 3 and 5. Each capillary tube has an expansion chambers 41 or 43 in the upper portion thereof. A metallic thread 45 or 47 which is welded half way up the capillary tubes 37 or 39 is used as reference level. It will be obvious that each capillary tube serves to determine the initial volume of the corresponding chamber before mixing, and the final volume after mixing, and to keep the pressure constant in the chambers so that there will be no influence of pressure in the determination of the volume of the mixture.

Turning back to the chambers 3 and 5 it will be real ized with reference to FIG. 1 of the drawings that the walls 49 and 51 thereof are quite thick and should therefore possess a very high thermic resistance. This also permits to easily provide threaded openings 53 and 55 which are used to engage threaded plugs 57 and 59 in which are mounted the capillary tubes 37 and 39 respectively all in the manner illustrated in FIG. 1 of the drawings.

Each chamber 3 and 5 is provided with a respective microburette 61 and 63. Since both microburettes are identical and are mounted exactly in the same manner we will restrict this description to mocroburette 63 which is used in cooperation with stock chamber 5.

Microburette 63 is made of a micrometer head 65 and a piston 67 which is attached 'to the head and has been machined with high precision to be capable of slidable displacement inside hollow cylinder 23. The two microburettes 61 and 63 are mounted exactly in the same manner on the body of the dilatometer 1 and consequently reference will only be made to microburette 63. Microburette 63 is fixed to the dilatometer 1 by means of a collar 69 which is screwed over a nipple 71 the latter being attached to the body of the dilatometer 1 in the particular manner illustrated in FIG. 1 of the drawings. For this purpose, the micrometer head 65 is attached with a cylinder 73 which is preferably made of brass and is provided with a flange 75. A gasket 77 made of Teflon (trademark for polytetrafluoroethylene) is mounted between flange 75 and the outer face 79 of the dilatometer 1. It is therefore possible to obtain an impervious joint by screwing the collar 69 over the nipple 71. On the outer faces of the gasket 77 there are two O-rings 81 and 83, and these will also increase the imperviousness of the joint. In order to obtain a tight joint between the gasket 77 and the piston 67 another -ring 85 is provided in the manner illustrated in FIG. 1. This 0-ring 85 can be made of Teflon or Viton (both terms are trademarks) or other materials depending on the nature of the solutions which are used.

The dilatometer l is immersed in a constant temperature bath which is contained in a plexiglass tub 87. The micrometer heads 65 of the microburettes 61 and 63 are outside the tub 87, as illustrated and are insulated from water by two rubber seals 89 and 91 which ensures at the same time a certain imperviousness. The plexiglass tub 87 is kept closed by means of a cover protector 93 which is also used to insulate the bath from the outside.

Referring now to FIGS. 1 and 4 we will describe in further details the temperature detector 11 and the heating element 13 in relation to the electrical controls illustrated in FIG. 4 of the drawings.

The heating element 13 is mounted on a Teflon plate 95 which is provided at the upper end of a plug 97 which is threaded as illustrated in FIG. 1 to fit inside threaded opening 99. Of course there is a suitable opening in the conical portion 7 of the chamber to insert the heating element 13 inside the chamber 5. The heating element 13 is connected to voltage source 101 by means of two stainless steel rods 103,105 which extent through plug 97 in the manner illustrated in FIG. 1 of the drawings. To measure the period of heating the heating element 13 and the voltage source 101 are coupled with a chronometer 107 and a relay 109.

As described above, the mixing chamber 5 comprises a temperature detector 11 which is used to measure the temperature inside mixing chamber 5. The temperature detector 11 is screwed in the lateral wall of the chamber 5 and is connected to a Wheatstone bridge 111. The Wheatstone bridge 111 is supplied with direct electrical current by means of the voltage source 113. A zero detector 115 indicates the equilibrium of the Wheatstone bridge. To determine with higher precision the temperature variations and to more surely determine the thermal equilibrium of the dilatometer, a recorder 1 17 is electrically connected at the output of the zero detector.

Turning now to the tub 86 the temperature of the water is tightly controlled by the constant temperature bath 122. The refrigeration unit 119 removes a constant amount of heat while the heater 121 operates on and off to maintain the temperature of the bath 122 constant. Circulation of the water into tub 86 is made possible by the provision of water circulation lines 123 and a force and succion pump 125. Consequently, the tempature in the tub 86 is maintained constant.

To operate the dilatometer 1, the mixing chamber 5 is filled with a known weight of a first liquid component and the stock chamber 3 is filled with a second'liquid component. To insert the liquid components, the plugs 57 and 59 are removed and the liquid components are inserted inside respective chambers 3 and 5 after which the plugs 57 and 59 are again placed in the openings 53,55. The dilatometer is then immersed in the tub 86. When the system has reached equilibrium, a known quantity of the second component is introduced into the mixing chamber 5 from the stock chamber 3 by operating the microburettes 61 and 63. By a simple reading of the dials of the microburettes 61 and 63 and proper calculation, the volume of mixing is readily obtained Simultaneously, if the system is endothermic, heat is added to the solution in the mixing chamber 5 by the heating element 13 to maintain the temperature constant. With a proper electrical system as illustrated in FIG. 4 of the drawings, the power added is easily calculated. The electrical circuit for measuring the voltage drop across heating element 73 and the amperage in the circuit are not illustrated. These data yield te heat of mixing whereby the apparatus is then used as a calorimeter.

The dilatometer was calibrated by determining the volume of mixing of two systems, namely, benzenecyclohexane and ethanol-n-heptane for which these experimental data are well known. FIGS. 2 and 3 show these results. The reproducibility is within 1.3 percent. Reference is also made to the following Tables I and 11.

TABLE I Volume of mixing of the binary system benzene-cyclohexane at 25C 1. concentration in benzene x, concentration in cyclohexane V in cmlg-mole With reference to FIG. 2, the known experimental data are taken from Powell, R..1., Swinton, F.L., .1. Ch. Eng. Data, 13, 260, (1968) and have been illustrated by black circles. The data obtained with the apparatus according to the invention are shown in white circles.

TABLE 11 Volume of mixing of the binary system ethanol-xyxlohexane at 25C x, concentration in ethanol x, concentration in cyclohexane V in cm'lg-mole With reference to FIG. 3, the known experimental data are taken from F. Pardo, Thesis Rennselaer Polytechnic Institute, Troy, New York, 1964 and H. Klapproth, Nova Octa Leopoldina, 9, 305 (1940), and have respectively been illustrated by black circles and white triangles. The data obtained according to the invention are shown in white circles.

We claim:

1. A semi-continuous dilatometer/calorimeter comprising:

a. a stock chamber to contain a first liquid;

b. a mixing chamber to contain a second liquid;

c. a small axial passage interconnecting said stock chamber and said mixing chamber;

d. a conical valve mounted in said axial passage;

e. means to introduce a portion of said first liquid from said stock chamber, through said small axial passage, to said mixing chamber wherein said portion of said first liquid is caused to be mixed with said second liquid;

f. said conical valve having a T opening to allow for expansion in the valve during preliminary heating or cooling of the mixture of liquids to bring it to a desired temperature;

g. means to determine the volume decrease of said first liquid in said stock chamber and the volume increase of liquid in said mixing chamber; and

b. means to determine heat changes in said mixing chamber.

2. A semicontinuous dilatometer/calorimeter according to claim 1, wherein said mixing chamber includes a magnetic agitator.

3. A semi-continuous dilatometer/calorimeter according to claim 1, wherein said stock chamber and said mixing chamber are each surmounted by a capillary tube, each capillary tube serving to determine the initial volume of a corresponding chamber before mixing said liquids and the final volume after said mixing, and to keep the pressure constant in said chambers.

4. A semi-continuous dilatometer/calorimeter ac cording to claim 1, wherein said means to determine said volume decrease and said volume increase com prises a microburette for said stock chamber and another microburette for said mixing chamber each said microburette having a piston entering a corresponding chamber to control the volume of liquid in said chamber.

S. A semi-continuous dilatometer/calorimeter according to claim 1, which comprises a bath mantained at a constant temperature in which said mixing and stock chambers are immersed.

6. A semi-continuous dilatometer/calorimeter according to claim 1, wherein said mixing chamber comprises temperature detecting means.

7. A semi-continuous dilatometer/clorimeter accord ing to claim 1, wherein said mixing chamber comprises heating means to maintain the temperature constant.

8. A semi-continuous dilatometer/calorimeter according to claim I, wherein said mixing chamber comprises refrigerating means to maintain the temperature constant.

Claims (8)

1. A semi-continuous dilatometer/calorimeter comprising: a. a stock chamber to contain a first liquid; b. a mixing chamber to contain a second liquid; c. a small axial passage interconnectinG said stock chamber and said mixing chamber; d. a conical valve mounted in said axial passage; e. means to introduce a portion of said first liquid from said stock chamber, through said small axial passage, to said mixing chamber wherein said portion of said first liquid is caused to be mixed with said second liquid; f. said conical valve having a T opening to allow for expansion in the valve during preliminary heating or cooling of the mixture of liquids to bring it to a desired temperature; g. means to determine the volume decrease of said first liquid in said stock chamber and the volume increase of liquid in said mixing chamber; and h. means to determine heat changes in said mixing chamber.

2. A semi-continuous dilatometer/calorimeter according to claim 1, wherein said mixing chamber includes a magnetic agitator.

3. A semi-continuous dilatometer/calorimeter according to claim 1, wherein said stock chamber and said mixing chamber are each surmounted by a capillary tube, each capillary tube serving to determine the initial volume of a corresponding chamber before mixing said liquids and the final volume after said mixing, and to keep the pressure constant in said chambers.

4. A semi-continuous dilatometer/calorimeter according to claim 1, wherein said means to determine said volume decrease and said volume increase comprises a microburette for said stock chamber and another microburette for said mixing chamber each said microburette having a piston entering a corresponding chamber to control the volume of liquid in said chamber.

5. A semi-continuous dilatometer/calorimeter according to claim 1, which comprises a bath mantained at a constant temperature in which said mixing and stock chambers are immersed.

6. A semi-continuous dilatometer/calorimeter according to claim 1, wherein said mixing chamber comprises temperature detecting means.

7. A semi-continuous dilatometer/clorimeter according to claim 1, wherein said mixing chamber comprises heating means to maintain the temperature constant.

8. A semi-continuous dilatometer/calorimeter according to claim 1, wherein said mixing chamber comprises refrigerating means to maintain the temperature constant.

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