The basic character of the protein molecule and the reactions of edestin with definite quantities of acids and alkalies.

  • Osborne, Thomas B. (Thomas Burr), 1859-1929.
Date:
[1900]
Catalogue details

Licence: In copyright

Credit: The basic character of the protein molecule and the reactions of edestin with definite quantities of acids and alkalies. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    That they are neutral bodies, like the carbohydrates, is not in harmony with what is known of them. Nevertheless, it appears to be generally assumed that a solu- tion containing protein matter, which shows neither acid nor alkaline reaction with litmus, is chemically neutral. Observations are on record which show that some protein solutions, when neutral to litmus, are acid to phenolphthalein and alkaline to lacmoid. It is also well known that a notable quantity of acid can be added to a protein solution before an acid reaction with tropaeolin, alizarine, or phloroglucin and vanillin appears. The fact that acids combine with protein bodies is, therefore, well known, and, in making preparations of these substances, the necessity of removing such acids has long been recognized. This has been supposedly accomplished by adding potassium or sodium hydrate or carbonate until the reaction with litmus becomes neutral. I am not aware that anyone has offered any evidence, however, that by this procedure this object is fully accomplished. It is of importance, therefore, to know whether litmus can be used to determine the point when all combined acid has been converted into neutral salts of potassium or sodium and all the protein substance has been set- free, or whether, as we know is the case when tropaeolin or lacmoid is used as an indicator, more acid still remains combined. Solutions in water of preparations of crystallized ovalbumin, in sodium chloride brine of excelsin, amandin, vignin, conglutin, glycinin, corylin, phaseolin and legumin, and in 759° Per cenk alcohol of zein, gliadin and hordein,* which were either neutral or acid when tested with a strip of sensitive, neutral litmus paper, capable of showing distinctly the presence of 0.25 cc. of centinormal hydrochloric acid in 10 cc. of water, when made neutral to litmus, were, in every case, still acid towards phenol- phthalein. With the exception of ovalbumin, these preparations had been made by the methods usually employed and had come in contact with no acid except that contained in the seeds from which they were obtained. The ovalbumin preparations were made both by Hopkins’ and by Hofmeister’s methods, the acidity of all of them being the same. * These protein bodies are described in Reports of this S . , 890 ,899 ; also Osborne. Amer. Chem. Jour., 13, 14 and 15 ! Joun J ^ Soc 16 17, 18, 19, 20 and 21 ; also Die Proteide, etc., Heidelberg, i»97-