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GRAHAM, THOMAS (1805-1869)
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See also:GRAHAM, See also: L. in 1855. He took ' eading See also:part in the See also:foundation of the London Chemical and See also:Cavendish See also:societies, and served as first See also:president of both, is 1 and 1846. Towards the See also:close of his life the See also:presidency of t Val Society was offered him, but his failing See also:health cause' ;to decline the See also:honour. Graham's work is remarkable at once for finality and for the simplicity of the methods employed 'ining most important results. He communicated papers t `losophical Society of Glasgow before the work of that so( 's recorded in Transactions, but his first published See also:paper, he Absorp- tion of Gases by Liquids," appeared in the An See also:Philosophy for 1826. The subject with which his name i :ominently associated is the See also:diffusion of gases. In his per on this subject (1829) he thus summarizes the kno' experiment had afforded as to the See also:laws which regulate ovement of gases. " Fruitful as the miscibility of gase. peen in in- teresting speculations, the experimental infor i we possess on the subject amounts to little more than the well-established fact that gases of a different nature when brought into contact do not arrange themselves according to their See also:density, but they spontaneously diffuse through each other so as to remain in an intimate See also:state of mixture for any length of See also:time." For the fissured See also:jar of J. W. See also:Dobereiner he substituted a See also:glass See also:tube closed by a plug of See also:plaster of See also:Paris, and with this See also:simple appliance he developed the See also:law now known by his name " that the diffusion See also:rate of gases is inversely as the square See also:root of their density." (See DIFFUSION.) He further studied the passage of gases by transpiration through See also:fine tubes, and by effusion through a See also:minute hole in a See also:platinum disk, and was enabled to show that See also:gas may enter a vacuum in three different ways: (1) by the molecular See also:movement of diffusion, in virtue of which a gas penetrates through the pores of a disk of compressed See also:graphite; (2) by effusion through an orifice of sensible dimensions in a platinum disk the relative times of the effusion of gases in See also:mass being similar to those of the molecular diffusion, although a gas is usually carried by the former See also:kind of impulse with a velocity many thousand times as See also:great as is demonstrable by the latter; and (3) by the See also:peculiar rate of passage due to transpiration through fine tubes, in which the ratios appear to be in See also:direct relation with no other known See also:property of the same gases—thus See also:hydrogen has exactly See also:double the transpiration rate of See also:nitrogen,'the relation of those gases as to density being as 1 :14. He subsequently examined the passage of gases through septa or partitions of indiarubber, unglazed earthenware and plates of metals, such as See also:palladium, and proved that gases pass through these septa neither by diffusion nor effusion nor by transpiration, but in virtue of a selective absorption which the septa appear to exert on the gases in contact with them. By this means (" See also:atmolysis ") he was enabled partially to See also:separate See also:oxygen from See also:air. His See also:early work on the movements of gases led him to examine the spontaneous movements of liquids, and as a result of the experiments he divided bodies into two classes—crystalloids, such as See also:common See also:salt, and colloids, of which See also:gum-arabic is a type —the former having high and the latter See also:low diffusibility. He also proved that the See also:process of liquid diffusion causes partial decomposition of certain chemical compounds, the See also:potassium sulphate, for instance, being separated from the See also:aluminium sulphate in See also:alum by the higher diffusibility of the former salt. He also extended his work on the transpiration of gases to liquids, adopting the method of manipulation devised by J. L. M. Poiseuille. He found that dilution with See also:water does not effect proportionate alteration in the transpiration velocities of different liquids, and a certain determinable degree of dilution retards the transpiration velocity. With regard to Graham's more purely chemical work, in 1833 he showed that phosphoric anhydride and water See also:form three distinct acids,- and he thus established the existence of polybasic acids, in each of which one or more equivalents of hydrogen are replaceable by certain metals (see See also:Anna). In 1835 he published the results of an examination of the properties of water of See also:crystallization as a constituent of salts. Not the least interesting part of this inquiry was the See also:discovery of certain definite salts with See also:alcohol analogous to hydrates, to which the name of alcoholates was given. A brief paper entitled " Speculative Ideas on the Constitution of See also:Matter " (1863) possesses See also:special See also:interest in connexion with work done since his death, because in it he ex-pressed the view that the various kinds of matter now recognized as different elementary substances may possess one and the same ultimate or atomic See also:molecule in different conditions of movement. Graham's Elements of Chemistry, first published in 1833, went through. several See also:editions, and appeared also in See also:German, remodelled, under J. See also:Otto's direction. His Chemical and See also:Physical Researches were collected by Dr See also: Additional information and CommentsThere are no comments yet for this article.
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