1. The quinhydrone method is applicable when the solution has a P
H less than 8.5.
2. The method gives no reliable results for the blood or for serum.
3. The method is adaptive for the PH measurement of the gastric juice and its titrimetry. The limit of its application is P
H=8.2.
4. The isoelectric point of albumin is found to be P
H=6.04, that of albumose 6.25, and that of peptone 5.54.
5. In order to titrate the total amount of HCl in a solu-tion containing one of these substances, the endpoint must be taken at its isoelectric point. It is therefore conceivable that the ordinary way of titrating the total HCl in gastric juice, using phenolphthalein as the indicator, includes a serious error.
6. The fixation of the hydrogen ion in a HCl solution by the intermixture of peptone follows the Freundlich adsorption formula.
This research was carried out at the suggestion and with the advice of Prof. P . Shoji of the Institute, and this paper was read before the second general meeting of the Nippon Biochemical Society on October 30, 1926.
When this paper was ready to be sent to this journal, Scukareff' s article just published (Biochem. Z.
180, 117, Jan. 1927) came to our notice in which he maintained that the total HCI of gastric juices is to be titrated to P
H=6.20
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