DE1051029B - - Google Patents

Description

GERMAN

Knowledge of the gas content of liquids is often a necessity in science and technology. To the Using the liquid phase analysis is in many cases very cumbersome or imprecise. On the other hand, it is Determination of the dissolved gases by examining the conditions in the associated gas phase, which is associated with the Liquid is in equilibrium, an easy and safer way. The inventive method on the The basis of Henry Dalton's law is suitable for doing justice to this task in general. It will detailed below for the control of dissolved gases in beer.

The carbon dioxide content of a beer is of great importance for its properties. Foaming capacity, Foam content, taste and dietary behavior are decisive due to the carbonic acid influenced.

It is therefore necessary in an ongoing K ontro lle about den_ £ Q ^ ^ eh t.4eaJBieresJn_den various stages Her manufacture perform .__ This is particularly important in bottled beer, as may occur through the Abfüilprozeß larger CO ₂ losses.

In addition to knowing the carbon dioxide content, the amount of air dissolved in the beer or its Oxygen content is important. The oxygen influences among other things significantly the colloidal and biological stability of the beer and its foam properties.

There are a large number of methods for the quantitative determination of carbon dioxide, which can be found in can classify gravimetric, titrimetric, volumetric and manometric. The principles of each Working methods are briefly described below:

1. Gravimetric methods. By heating the beer, the carbonic acid is expelled and absorbed in alkali. The entrained water is absorbed beforehand (CaCl ₂ or H ₂ SO ₄ ). The amount of carbonic acid is determined by the increase in the weight of the alkali. These methods require cumbersome equipment and lengthy, precise work. The results are relatively accurate.

2. Titrimetric methods. The carbon dioxide in the beer is bound by adding caustic soda. Man can now either back-titrate directly with H Cl against phenolphthalein or the carbonic acid by acidification make free. In the latter case, they are absorbed in barite water and titrated. The results are ever more or less certain after modification of the method. The way it works is very cumbersome. Be made more difficult these analyzes by the presence of free acids in the beer.

3. Volumetric methods. With these methods, the carbonic acid is also bound with caustic soda and sets them free again by acidification. That

Method and device
for quantitative determination
gases dissolved in liquids,
especially of carbon dioxide in beer

Applicant:

Scientific station for brewery
in Munich e. V. _f
Munich 19, Romanstr. 41

Dr. Ernst Paukner, Munich, has been named as the inventor

Carbon dioxide gas is collected in a burette and measured. It can be proportionate this way determine exact values. The disadvantage of these methods lies in the fact that an exactly working apparatus is required (Van Slyke burette), which can only be properly operated by trained personnel can.

4. Manometric method. The basis for this method is formed by Henry's Daltelian law, according to which At a given temperature, the concentration of the gas dissolved in a liquid corresponds to the partial pressure of the gas in is proportional to the gas phase, provided that there is a state of equilibrium.

Various modifications of the manometric method are already known, but there are important ones Determination variables are not or are not correctly recorded by measurement technology, z. B. the partial pressures of the rest Gases (also the vapor pressure of the beer), also the consideration of the connected rooms of the pressure gauge and the specific solubility of beer and not water. The known manometric measuring methods therefore do not provide error-free results.

The method according to the invention for the quantitative determination of dissolved gases in liquids is also a manometric method. The apparatus to be used is simple; H. even by untrained workers exactly to use.

The determination ^ Since jeUöclTtm beer mostly * neberr CO ₂ Tidch considerable amounts of dissolved air of beer, in particular-in-F4aschenbier dissolved CO ₂ ^ afFeinFacnT ^r If it were b ei dissolved in the beer gas to pure CO ₂ Tian punching , the total pressure in the gas phase (empty space of a

809 750/268.

Claims (1)

I 051 029 bottle) increased. You will therefore make an error if you use the measured total pressure as the basis for calculating the CO2 content. For an accurate pressure measurement of the partial pressure of CO2, it is essential to know the partial pressure of the other gases - nitrogen, oxygen and the vapor pressure of the beer. To determine the pressure, it must also be taken into account to what extent the connected rooms of the pressure meter change the equilibrium pressure due to their volume. Another source of error lies in the previous assumption that the same solubility ratios exist for beer with regard to CO2, N2 and O2 as for water. The method according to the invention is characterized in that the saturation pressure prevailing in the gas phase is measured, then the gas phase is quantitatively displaced by introducing a displacement liquid, whereupon the partial pressure of the individual gases is calculated by volumetric gas analysis with the aid of the original saturation pressure and the associated gas content of the Liquid can be determined. In the method according to the invention, the following errors are eliminated, which results in technical progress compared to the known. a) By filling the spring tube of a manometer with a viscous mass that is insoluble in beer and does not change the accuracy of the manometer's display, the connection of harmful space to the gas phase (empty space in a bottle) is prevented. In the known methods, no filled manometer spring tube is used. The pressure measurement with an unfilled pipe must therefore give an incorrect result. b) According to the previously known method, the total air content of the bottle is used to determine the partial pressure of the "Luit" - that is, the proportion dissolved in the liquid plus the "air" in the empty space. This mode of operation is flawed because, according to Henry-Dalton's law, only the gas phase in equilibrium may be used to determine the partial pressure. Certain components of beer are oxidized by air. In this way, the ratio of nitrogen to oxygen in the "air" dissolved in the beer and in the gas phase changes. The “air” fraction found using the previously known method is therefore incorrect, since it is no longer air in the physical sense. For the assessment of the oxidation state of a beer it is of particular importance how high the oxygen content of a beer is, but this cannot be determined with the previously known method. · C) According to the previously known method, only one factor was specified for the difference in the solubility ratios of CO2 in beer compared to water, namely that for CO2. The solubility ratios of the other gases were not determined experimentally. In contrast, the method according to the invention is based on the precise measurement of the solubility ratios for the gases CO2, N2 and O2 in the temperature range between 0 and 80 ° C. for water and beer. The method according to the invention and the device for carrying out the method are illustrated in the drawing, for example: A container 1 (e.g. bottle with crown cork closure) contains the gas phase 2, which is in equilibrium with the liquid phase 3. A piercing mandrel 4 is sealed in this gas phase through a rubber press seal 5 inserted. The piercing mandrel 4 has two channels 7 and 8. Channel 7 is to be closed off by valve 9. A manometer 11 with a filled spring tube is connected to channel 8. The duct 8 can be closed off from the outside by means of the tap 10. With the taps 9 and 10 closed before the introduction of the mandrel 4, the overpressure prevailing in the gas phase can be read on the manometer 11. If you now open cock 10, part of the gas phase can flow into a (not shown) apparatus for gas analysis (Orsat) until the pressure is equalized through channel 8. In order to determine the gas phase quantitatively, sealing liquid is pressed in through the open cock 9 and the channel 7 and the remaining gas phase is likewise passed through the channel 8 and the cock 10 into the gas apparatus. From the percentage by volume of the individual gases in the total gas phase, you can use. With the help of the original absolute equilibrium pressure, the partial pressure of the individual gases can be calculated and the associated gas content of the liquid can be determined from appropriate solubility tables. Example The determination of the CO2, N2 and O2 content of a bottled beer is given as an example for the application of the method and device described. After drilling through the crown cork of a 0.5-1 bottle in a gas-tight manner using the mandrel, a gas pressure of P = 1900 Torr abs is established in the empty space of the bottle LR at 20 ° C. (corrected value) measured. After the gases in the empty space have been completely displaced, 2.7 ml of N2 and 0.3 ml of O2 (0 ° C / 760 Torr) are found. After reduction to normal conditions (0 ° C / 760 Torr), the gas mixture in the empty space comprises: 15-1900-273 LRn = -ZT ^ —— = 34.9 ml (I) 760 293 The partial pressure of nitrogen is 2.7 ■ 100 · 1900 2 = 349 = 147 (Torr) The partial pressure of oxygen is 0.3 x 100 x 1900 P O2 34.9 = 16 (Torr) (III) To get the partial pressure of carbonic acid, the sum of (II) + (III) to deduct from the gas pressure p: PCO1 = P "2 U2, 1900- (147 + 16) = 1737 (Torr). (IV) The carbon dioxide, nitrogen and oxygen content of the beer can be determined using the values from (IV), (II) and (III) corresponding solubility tables (calculated with the associated Bunsen or Ostwald sorption coefficient for 20 ° C) The result is a CO2 content of 1870 ml / 1; the result is an N2 -Content of 3.80 ml / 1; the result is an O2 content of 0.52 ml / 1. P Λ TENT Λ NSPRC CHE: 1. Henry-Dalton's method for the quantitative determination of gases dissolved in liquids Law, characterized in that the pressure prevailing in the gas phase is measured, then either an aliquot part of the gas phase flows off by its own pressure or by introducing a Displacement liquid, the gas phase is quantitatively displaced, whereupon by volumetric gas analysis the partial pressure of the individual gases is calculated using the original equilibrium pressure