94 THE COLOUR REACTIONS OF GASTRIC JUICE. [BOOK II. 



when employed in the investigation of gastric juice as ordinarily 

 obtained on account of the presence of proteids in it. The same 

 remark applies to OO tropaeolin, which has been employed in the 

 investigation of gastric juice, but which is not to be relied upon in the 

 presence of the organic matters which it contains. 



00 Tropseo- A solution of this body (the potassium salt of 



phenyl amido-azobenzene-sulphonic acid) is made in 

 alcohol. A few drops of the yellowish solution are added to the 

 liquid to be tested. If a mineral acid be present, a fine pinkish red 

 colour is developed, but if a dilute organic acid, no change occurs or 

 the solution merely becomes of a more reddish yellow tint without 

 shewing any of the pink of the HC1 reaction. * 



This reagent may be employed in a different manner. Drops of 

 a saturated solution are allowed to evaporate on a porcelain slab at 

 40 C., and, whilst at this temperature, a drop of the liquor to be 

 tested is added, when on evaporation a violet stain is left if HC1 be 

 present. "006 per cent, of pure hydrochloric acid can thus be 

 detected. 



Con o Red colouring matter, which is soluble in water, 



furnishes an exceedingly delicate test for free acids, and 

 for their detection it may be employed in aqueous solution or by 

 saturating filter paper in it and then drying it. 



Free hydrochloric acid even in very dilute solutions, changes the 

 red to an intense blue colour, whilst organic acids cause it to assume 

 a violet tint. 



This reaction appears to the author one of the most sensitive and 

 most useful which have been suggested for the detection and dis- 

 crimination of the acids of the gastric juice. 



Emerald- Papers stained with this colouring matter are not 



affected by solutions of organic acids, however concen- 

 trated, whereas dilute solutions of hydrochloric acid change the 

 bluish-green tint to a grass-green colour. 



pnioro- " The reagent recommended by Gimzburz contains 



giucin and 2 grms. of phloro-glucin and 1 gramme of vanillin 

 dissolved in 100 c.c. of alcohol. When hydrochloric 

 acid is added to this solution, it deposits beautiful red crystals. For 

 the detection of the acid in gastric juice it is employed thus : To 

 the fluid to be tested for acid an equal quantity of the reagent is 

 added, and the mixture evaporated in the water bath. The presence 

 of hydrochloric acid is shewn by a delicate rose-red tint on the 

 surface of the porcelain dish. In this way so little as O'OG per cent. 

 of the acid is discernible, and the reaction is not impeded by organic 

 acid, albumin or pepton 1 ." 



1 v. Jaksch, 'Clinical Diagnosis.' Translated from the 2nd Germ. Edition by James 

 Cagney, M.A., M.D. &c. London, Charles Griffin and Co., 1890, see pages 98 and 99. 



