Voges & Proskauer [1898] observed that when strong alkali was added to broth cultures of certain species of bacteria there developed, after an interval of time, a pink colour. Subsequently the work of Harden [1906] and of Harden & Norris [1911] established that the chemical reaction responsible was one between diacetyl and creatine (or certain similar substances). Attempts to make the reaction quantitative [Walpole, 1911; Eggleton & Eggleton, 1928] were only partially successful. The reaction was further studied by Duliere [1929], Lang [1932] and Muller [1935], but it was the discovery by Barritt [1936], that o-naphthol greatly intensifies the colour, which made it possible for the first timne to use this reaction as a means of estimating either creatine or diacetyl. The present paper presents some additional facts about the reaction and methods of estimation based on it.
IN a study of the significance of phosphorus in muscle contraction (which will be reported separately) some observations were made which throw a doubt on the chemical results of some earlier workers. Evidence is given in this paper to show that the supposed inorganic phosphate of muscle is in certain conditions mainly organic phosphate of a very labile nature, which is so unstable in acid solution that it is hydrolysed during the estimation of the inorganic phosphate by the methods of Neumann, Embden [1921] or Briggs [1922]. Estimations performed in neutral or slightly alkaline solution, such as the Bell-Doisy method [1920], or precipitation by magnesia mixture, give results approximating to the truth, provided the muscle extract has not previously been exposed to the action of acid.Briggs' method itself can be used to demonstrate the existence of this unstable phosphoric ester. Details of the method are given elsewhere: it suffices for the moment to say that after the addition of the appropriate reagents to a solution containing phosphate a blue colour develops, which rises to a maximum in about 30 minutes, after which time colour comparisons are usually made. It is easy to show that the rate of development of this blue colour follows a simple exponential law, intensity at time t = c = P (1 -e-kt), where P is the final colour which measures the phosphate. The constant k has the value 0-12 (time measured in minutes). It follows mathematically (and can be proved experimentally) that in comparing two quantities of inorganic phosphate the ratio of the colour intensities will be the same at whatever time the comparison is made. If the colour ratio be plotted against time the result is a straight line parallel to the time axis (lines AB and CD in Fig. 1
1. An apparatus is described for measurement of both the solubility and the diffusion constant of a gas in a liquid solvent.
2. Attention is drawn to the possibility of supersaturation of a gas in a solvent when "equilibration" is hastened by shaking.
3. The solubilities and diffusion constants of H2 and 02 in olive oil and tetrahydronaphthalene are recorded, also the solubility and diffusion constant of N2 in olive oil, tetralin, oleic acid, and liquid ethyl palmitate.
4. The behaviour of the gases N2, H2, and 02 in lard has been studied.
5. It is shown that H2 can dissolve in, and diffuse through, stearic acid crystals at 25° C. though not in crystals of o‐chloro‐nitro‐benzene.
6. Crystalline ethyl stearate and palmitate can dissolve CO2 but not nitrogen.
7. The bearing of some of these results on the movement of dissolved nitrogen in the body is discussed.
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