Observations on the changes produced in the blood &c / by Charles J.B. Williams.

Date:
[1835]
Catalogue details

Licence: Public Domain Mark

Credit: Observations on the changes produced in the blood &c / by Charles J.B. Williams. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    difference between liquid silica and liquid albumen; the former cannot be evaporated to dryness without losing its solubility: liquid albumen may be dried at any temperature below 150®, and the transparent solid thus formed is not only soluble again into liquid albu- men, but, whilst dry, it may be heated to 212®, without losing its solubility. This fact proves that neither a nascent state, nor one of minute division, is necessary to its solution, and that a change of either the combination or arrangement of its particles takes place before albumen passes from the liquid to the coagulated state. This corresponds with the explanation given further on*.] MM. Prevost and Dumas, of Geneva, in a memoir rich in observations of great value to the physiologist, have recently pointed out a number of properties which would seem to rank coagulated albumen as an acid capable of com- bining with bases; and render it pro- bable that in serum and white of egg it exists in union with soda, which makes it soluble in water. Thus any thing which is capable of abstracting the soda will cause the precipitation of solid al- bumen. This effect is produced by acids and alcohol; the action of the for- mer is obvious, and that of the latter probably depends on the affinity which caustic soda exerts for this vehicle, presenting a phenomenon the converse of that resulting from the action of water on some metallic salts. In con- firmation of this view, I find that albu- men shows stronger marks of alkalinity if a little alcohol has been added to coagulate it. [I think, however, that this effect of alcohol may with more rea- son be ascribed to its affinitv for water as well as for soda. Alcohol in like manner precipitates gums from their solution in water.] But what sets the acid nature of albumen in a clearer light, is the effect of galvanism on it. To Mr. Brande we owe the discovery that when white of egg is sub- jected to the galvanic influence, coagu- lated albumen is deposited at the posi- tive pole, while caustic soda may be detected at the negative pole. Prevost and Dumas observe, that when this ex- periment is performed with wires of an oxidable metal, the albumen forms a * Exnmen.du Sang. &c. Bibliotli. Universellc, lomcxvi. 1821. compound with the oxide. [Lassaigue, however, attributes the coagulation of albumen at the positive pole to free muriatic acid resulting from the de- composition of the muriate of soda com- bined in albuminous fluids; but the quantity of muriatic acid thus developed is too small to produce such an effect. Galvanism is a far more delicate test for albumen than muriatic acid is, and accumulates at the positive wire a coa- gulum of albumen from the weakest solutions, which it could not do if liquid albumen were not (to use the language of Faraday) an electrolyte compound ; for single ions, or uncombined bodies, are quite indifferent to an electric cur- rent.] This view of the nature of albumen receives some support from some ex- periments which I have made to deter- mine how far it is capable of neutra- lizing alkalies. Thus, to the white of egg, diluted with three times its bulk in water, weak muriatic acid was added, to such extent as exactly to neutralize the excess of alkali, without occasion- ing any coagulation. Some albumen similarly diluted was coagulated by muriatic acid, and pure potass very cautiously added until the coag'ulum was re-dissolved; the solution, when tested at this period, scarcely exhibited alkaline qualities. A similar result was obtained with the coagulum by beat. [Very similar results have since been obtained by Berzelius, who neutralized the alkali of serum by means of acetic acid, without causing any coagulation. He also formed a liquid albumen arti- ficially, by dissolving fibrine or coagu- lated albumen in a solution of potass, and neutralizing the excess of alkali by acetic acid. The liquid albumen thus formed was coagulable by acid and alcohol, but not by heat.] On this view, MM. Prevost and Du- mas attribute the coagulation of albu- men by heat to the saturation of the alkali by carbonic acid; which they conceive to be formed bjr the decompo- sition of a small quantity of the albu- men. It has been ascertained by Four- croy, that an egg is incapable of form- ing a firm coagulum unless it has for some time been exposed to the air. This exposure is attended with an absorption of oxygen; and I am inclined to be- lieve that this oxygen, at a high tem- perature, abstracts a portion of carbon from the albumen, and thus carbonic