Copper-ferrocyanide

The shortage of tungsten and molybdenum during the 1930s in Germany necessitated the use of copper ferrocyanide as anion. Some of these salts have maintained their commercial position to the present time. Besides, silicomolybdates are also used to produce this type of pigments. 

Copper ferrocyanide complex salts, which are occasionally used, are derived from copper-l-hexacyano-iron-2-acid HCu3[Fe(CN)6], Three equivalents of copper are required for each unit of ferrocyanide, which furnishes the following general pigment structure ... 

The corresponding copper ferrocyanide salts of basic dyes are obtained by treating potassium ferrocyanide K4[Fe(CN)6] with sodium sulfite. Dissolved to-... 

CF represents copper ferrocyanide (copper-l-hexacyano-iron-II-acid). 

The cation-exchange capacity of the copper ferrocyanide gel used was found to be about 2.60 meq/g and its anion-exchange capacity about 0.21 meq/g. In all cases of various doses of gel used and types of anionic surfactants being removed, the tests indicated that a batch contact time of about 12 hours was sufficient for achieving maximum removals. Trials with various fractions of particle size demonstrated that both uptake and desorption (important in material regeneration) were most convenient and maximized on 170-200 BSS mesh size particles. Also, the adsorption of anionic surfactants was found to be maximum at pH 4 and decreased with an increase in pH. 

In the Berkeley and Hartley method, a porous tube with a semipermeable membrane such as copper ferrocyanide deposited near the outer wall, and a capillary tube attached to one end contains the pure solvent, The solution surrounds the tube and is enclosed in a metal vessel to which a pressure may be applied which is just sufficient to prevent the flow of solvent into the solution. Berkeley and Hartley also developed a dynamic method for measuring osmotic pressure. 

Data collected with membranes of this type played an important part in the formulation of present-day solution theory—so much so that the authors have used this theory without hesitation to compute osmotic pressures of solutions whose osmotic pressures have never been precisely measured. Such a solution is sea water. The copper ferrocyanide membrane is leaky to solutions of strong electrolytes. Some data have been obtained on weak solutions of strong electrolytes by the Townend method (16), but no one has made precise measurements on the osmotic pressure of sea water. 

Potassium copper ferrocyanide has a characteristic red-brown color which originates from an absorption at 20,200 cm.-1. Following the above assignments, we can reasonably attribute this to an iron(II) - copper(II)... 

Rigamonti, R. Structure of Cupriferrocyanides I. Copper Ferrocyanide and Potassium Copper Ferrocyanide. Gazz. chim. Ital. 67, 137 (1937). 

The pores m a copper ferrocyanide membrane are exceedingly fine, ranging from 8 to 60 jjLji in diameter, the average being from 15 to 20 fifxJ The osmotic action is not due to a selective mechanical filtration, but to selective adsorption on the surface of the membrane. Hence such membranes as have the smallest pores and expose the greatest superficial area are the most efficient semipermcable structures. 

Copper ferrocyanide may be obtained in colloidal form of high chemical purity by prolonged dialysis of the solution obtained by mixing equivalent solutions of sodium ferrocyanide and copper chloride (or sulphate).8... 

The molecular weight of colloidal copper ferrocyanide has been calculated 9 as 700,000. 

Van Dyke red. A brownish-red pigment consisting of copper ferrocyanide sometimes used to refer to red varieties of ferric oxide. 

Copper ferrocyanide silicate Lead silicate Peptone tannate Barium sulphate Silver chloride... 

Other sugars were also employed, and in later papers an account is given of similar very accurate measurements both of osmotic pressure and lowering of vapour pressure, due to calcium ferrocyanide m water, this salt being a very soluble one, and one which at the same time is practically stopped by the copper-ferrocyanide semi-permeable membrane (Earl of Berkeley, E G J Hartley, and C V Burton, PM Trans, 209 A, 177, 1909 Dilute solutions ofthe same solute were also investigated by the Earl of Berkeley, E G J Haitley, and J Stephenson, ibid, p 319 ) For details the reader is again referred to the ongmal papers The object of the work referred to was to test Porter s equation This equation will be taken later... 

In a later paper (Trans Chem Soc, 105, 1941 (1914)) Donnan and Allmand investigated the distribution equilibrium of potassium and chlorine 10ns across a copper ferrocyanide membrane The results, whilst confirming the theory, were complicated by the uncertainty as to the manner of ionisation of potassium ferrocyanide It was considered that this difficulty would be overcome if solutions of two ferrocyamdes were employed on the two sides of the membrane, especially if these salts were ionised to the same extent This case was investigated by Donnan and Garner (Trans Chem Soc, 115, 1313 (1919))... 

Copper ferrocyanide 4Odd CuFeCy Feirocyanlde of copper m ussiate of copper. 

Copper. Hydrogen sulphide precipitates black copper sulphide in presence of dilute hydrochloric acid. Salts give green flame. Potassium ferrocyanide gives brown precipitate of copper ferrocyanide in presence of acetic acid. 

Pfeffer s research had been on osmotic pressure. It had been well established from early in the eighteenth century that when a solution is separated from pure water by a semipermeable membrane such as a bladder, the water permeates the membrane and dilutes the solution, setting up a pressure if the volume of the latter is prevented from increasing. This pressure was termed osmotic pressure. Pfeffer in 1877 was able, by depositing copper ferrocyanide on the walls of a porous pot, to prepare semipermeable membranes that were permeable to water, but were not permeable to dissolved sugar. Using these semipermeable membranes, he was able to measure the osmotic pressures of solutions. ... 

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