Patent GB-876031-A (GB)
Title: Improvements in or relating to methods of testing and controlling the progress of chemical reactions
Inventor: MCGILVRAY DONALD IAN
IPC: G01N25/48
Filed: 1959-03-16
Abstract: <PICT:0876031/IV (a)/1> <PICT:0876031/IV (a)/2> The concentration of a chemical substance in a mixture, e.g. a solution, is determined by feeding a portion of the mixture to a vessel where it is contacted with a controlled amount of a substance with which it reacts exothermically or endothermically, measuring the temperature in the vessel and comparing this with the temperature of the initial mixture or of the contents of a second vessel to which a proportionate amount of the mixture is fed without reaction with the other substance, thus eliminating errors due to temperature fluctuations of the substances. This method is particularly suitable for determining the concentration of sulphuric acid in the coagulating baths for making regenerated cellulose fibres and films.  In Fig. 1 the acid bath is contained in a vessel 1 from which proportionate amounts can be delivered into two other vessels 3 and 4, one of which contains aqueous alkali and the other water supplied from 5 and 6. Thermojunctions 7 and 8 in these vessels produce an E.M.F. which is proportional to the difference between the respective temperatures, which in turn is dependent on the heat of reaction between the acid and alkali.  Provided that there is sufficient alkali to react with all the acid present, the reading of the galvanometer 9 will be proportional to the amount of acid in the bath.  The galvanometer current can be backed off to employ the most suitable part of the scale for any particular range of acid concentrations.  The vessels 5 and 6 can also be provided with thermojunctions in series with the other two, to allow for fluctuations in the temperature of the water and alkali (Fig. 2, not shown).  In a modification (Fig. 3) acid from 1 and alkali from 6 are fed into a reaction vessel 4 and the temperatures in the three vessels are combined algebraically to show the heat of reaction.  In many cases the alkali can be replaced by water and the heat of dilution of the acid measured.  The galvanometer current can be used to give a permanent record or to regulate the amount of acid in the bath.  The measurements can be made continuously or by delivering measured batches.  The acid liquid can be diluted and/or cooled to a known extent before the determination.  The amounts of acid, alkali and water used may be equal or may be in known ratios to one another.  In the method of Fig. 1 a reaction may be arranged to occur in both vessels 3 and 4.ALSO:<PICT:0876031/III/1> <PICT:0876031/III/2> The concentration of a chemical substance in a mixture, e.g. a solution, is determined by feeding a portion of the mixture to a vessel where it is contacted with a controlled amount of a substance with which it reacts exothermically or endothermically, measuring the temperature in the vessel and comparing this with the temperature of the initial mixture or of the contents of a second vessel to which a proportionate amount of the mixture is fed without reaction with the other substance, thus eliminating errors due to temperature fluctuations of the substance. This method is particularly suitable for determining the concentration of sulphuric acid in the coagulating baths for making regenerated cellulose fibres and films.  In Fig. 1 the acid bath is contained in a vessel 1 from which proportionate amounts can be delivered into two other vessels 3 and 4, one of which contains aqueous alkali and the other water supplied from 5 and 6. Thermojunctions 7 and 8 in these vessels produce an E.M.F. which is proportional to the difference between the respective temperatures, which in turn is dependent on the heat of reaction between the acid and alkali.  Provided that there is sufficient alkali to react with all the acid present, the reading of the galvanometer 9 will be proportional to the amount of acid in the bath.  The galvanometer current can be backed off to employ the most suitable part of the scale for any particular range of acid concentrations.  The vessels 5 and 6 can also be provided with thermojunctions in series with the other two, to allow for fluctuations in the temperature of the water and alkali (Fig. 2, not shown).  In a modification (Fig. 3) acid from 1 and alkali from 6 are fed into a reaction vessel 4 and the temperatures in the three vessels are combined algebraically to show the heat of reaction.  In many cases the alkali can be replaced by water and the heat of dilution of the acid measured.  The galvanometer current can be used to gave a permanent record or to regulate the amount of acid in the bath.  The measurements can be made continuously or by delivering measured batches.  The acid liquid can be diluted and/or cooled to a known extent before the determination.  The amount of acid, alkali and water used may be equal or may be in known ratios to one another.  In the method of Fig. 1 a reaction may be arranged to occur in both vessels 3 and 4.