Physiological histology, methods and theory / by Gustav Mann.

  • Gustav Mann
Date:
1902
Catalogue details

Licence: Public Domain Mark

Credit: Physiological histology, methods and theory / by Gustav Mann. Source: Wellcome Collection.

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    of charge can be held by all other monovalent radicals, while double the amount is carried by a divalent radical and so on. When the valency of a metal alters, for example, when the divalent ferro-ion becomes the trivalent ferri-ion, an extra charge of electricity is given to the ferro-ion, changing its nature thereby completely. It is readily seen that the greater the charge of an ion, the greater will also be its tendency to part with some of its load, hence the great readiness with which osmium or ruthenium tetroxides become reduced by organic bodies. The valency of electrically active ions, as already mentioned above, p. ii, is expressed in monovalent an-ions by a dash, and for mono¬ valent kat-ions by a dot ; for divalent ions two dashes or two dots are given, and so on. Thus : Fe’* means the electrically charged divalent ferro-ion, while Fe*'* indicates the trivalent ferri- ion, one gram molecular weight of which carries three times 96,500 coulombs. Although ions of the same valency have the same carrying power as regards electricity, yet their affinities for electricity vary ; thus the monovalent hydrogen will rob the monovalent mercury of its load, and in its turn has to give up its charge to potassium, which has a still greater electro-affinity. The following table of electro-affinities is taken from the very clear account found in Abegg and Herz’s book \ Electro-affinities of some kat-ions arranged in order of their strengths: K*, Na*, Li*, Ba*7 Sr**, Ca*\ Mg**, Co**, Ni**, Pb**, H*,Cu**, Ag*, Hg*, Pt* Al***, Mn**, Zn**, Cd“, Fe**, , Au . Electro-affinities of some an-ions : (F, NO/, CIO3O (or, SO/0 Br', r, R2BOs\ OHO ON', O'O S. PO/'O C03, CrO/0 SiO/0 SHO Solutions of electrolytes containing many ions per unit of volume are obtained with compounds of the strong kat-ions K*, Na*, and Li* with all an-ions; and further with the soluble combinations of Ba**, Sr**, Ca**, Mg**, Mn** ) (NO/ Zn**, Fe**, Co**, Ni**, Pb**, H* } with i F, CIO BP, V Hg, Ag* j {SO/' Only a few ions per unit of volume are formed by HgCl2, Hg(CN)2, Fe(CNS)s, Fe(C2Hs02)8, NH4OH, H2S, HCN, H2C03. As long as no electrical current flows through a solution contain¬ ing equivalent numbers of negative and positive ions, these will be in a state of intimate mixture ; but the passage of an electrical stream will set the — ions travelling towards the + pole, and the -f ions on their way towards the negative pole. The rate of migration has already been given on pp. 10 and 11. 1 Abegg and Herz, Chemisches Practikum, Vandenhoek and Ruprecht, Gottingen, 1900. (English translation, Macmillan.)
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