A critique of certain methods of gastric analysis / by David L. Edsall.

  • Edsall, David Linn, 1869-1945.
Date:
[1901]
Catalogue details

Licence: In copyright

Credit: A critique of certain methods of gastric analysis / by David L. Edsall. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    mixtures are concerned. Now as to Topfer's method, Strauss found that the results for free HC1 obtained by this method (dimethylamidoazobenzol) were nearly always decidedly higher than those obtained with phloroglucin-vanillin. I had the same results. Phloroglucin-vanillin being generally considered to give accurate results, the proper conclusion seemed to be that the results with the dimethylamidoazo- benzol were variable and usually too high. Those who adhered to Topfer's method claimed that this was not true. I think the results with phosphotungstate and phloroglucin-vanillin, used on the same specimen, while demonstrating the accuracy of both these tests, show the inaccuracy of dimethylamidoazobenzol as an indicator for free HC1. When one inaccurate indicator is used in estimat- ing the free HC1, when the combined HC1 is esti- mated by using as an indicator alizarin, which gives an end reaction which is extremely difficult to recog- nize and very likely to lead to error (if indeed it can be considered to be accurate at best) and when the method includes the use of three different indicators, it is practically impossible to obtain accurate results, for it is well known that an error attends upon the use of practically every indicator, and that this error varies for each indicator. The errors of three indi- cators are therefore introduced in this method, and this is in itself sufficient to make the method probably unreliable. The method suggested by Hewes is in brief as follows: The total acidity is estimated as usual by using phenophthalein as an indicator, but Hewes recommends that it be continued until a deep-red color is obtained rather than stop at the first appear- ance of pink. The free acidity is then estimated by titrating with dimethylamidoazobenzol until the end reaction is nearly obtained., when tropselin is used