Method Of Hehner And Seemann

1 - 10 c.c. of the filtrate are neutralized with a decinormal standard solution of sodium hydrate, evaporated to dryness over the water bath, and calcined over the flame. The residue consists of neutral salts + carbonate of sodium. The latter is determined in the following manner: The residue is washed with hot water and filtered as long as the filtrate gives an alkaline reaction. This filtrate is then titrated with a decinormal standard solution of sulphuric acid, until a slightly acid reaction arises. The amount of the decinormal standard sulphuric-acid solution used corresponds to the amount of inorganic acid. The difference between this figure and the figure of the total acidity expresses the amount of free and combined hydrochloric acid.

Method Of Hayem And Winter

2 - The principle of this method consists in the determination, first, of the total amount of chlorides; second, of the fixed chlorides (chloride salts); and third, of the amount of chlorides combined with acids. Proceed as follows: In each of three porcelain dishes (a, 6, c) place 5 c.c. of the filtrate. To dish a an excess of carbonate of sodium is added. All the three dishes are then evaporated to complete dryness over a water bath. A solution of carbonate of soda is now added in excess to dish b and the contents are again evaporated to dryness. All the three dishes are then calcined over a Bunsen burner, but the heating should not be carried too far, and the calcination should be arrested when there are no more points of ignition. To dishes a and b a slight excess of pure nitric acid is added and then some distilled water. After boiling the contents of these two dishes (a and 6), they are thrown on a filter. Dish c is treated with boiled water alone and then also filtered. The amount of chlorides contained in the three different filtrates is then determined by a decinormal standard solution of nitrate of silver in the presence of yellow chromate of potassium as indicator.

Dish a shows the total amount of the chlorides (T = chlore total), b = combined + fixed chlorine, and c=F = chlore fixe; b - c corresponds to the amount of combined hydrochloric acid = C = chlore combine; a - b corresponds to the amount of free hydrochloric acid = H = free hydrochloric acid. The total acidity is determined by titration with a decinormal sodium-hydrate solution and phenolphthalein as mentioned above.

1Seemann: Zeitschr. f. klin. Medicin, vol. v., p. 272.

2Hayem et Winter: "Du Chimisme Stomachal," Paris, 1891, p. 72.