Page:Text-book of Electrochemistry.djvu/55

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��38 LAWS OF AVOGADRO AND VAN'T HOFF. chap. hi.

potassium ferrocyanide, the coefiScients of these latter solutions l)eing set equal to 1 : —

��u

Potassium ferrocvanide

�Ammouium sulphate.

�<>upric nitrate. ..

�('opper acetate . ..

�Copper chloride. .

�^fagnoaium sulphate.

�Zinc sulphate. ..

�Copper sulphate. .

�Ethyl alcohol. ..

��usO-S

��n = 0'i

��Further Experiments on Osmotic Pressure. — Adie {9) has in a large measure overcome the technical difficulties in connection with osmotic experiments ; he has determined the osmotic pressure of salt solutions, and obtained results which agree remarkably well with the requirements of the theory, so long as dilute solutions are used. For concentrated solutions, however, it has not yet been possible to prepare jjerfect semi-permeable membranes.

In tliis respect the experiments of G. Hedin (7) and Koppe (10) are interesting. A certain quantity of blood was added to equal quantities of various salt solutions placed in tubes in a centrifugal machine. The blood corpuscles collected together in the end of the tube in a cylindrical mass from the height of which the total volume of corpuscles added to the salt solution could be estimated. This volume was found to be t^e smaller the higher the osmotic pressure of the salt solution. Hedin and Eoppe obtained results for the osmotic pressure of different solutions which were in close agreement with theory.

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