301- Mr. T. Grali am on Liquid Diffusion applied to Analysis. 



This blue liquid is quite incapable of passing through the dialyser, 

 and is equally colloidal with ordinary prussian blue. So also is 

 basic prussian blue prepared by the spontaneous oxidation of 

 precipitated ferrocyanide of protoxide of iron. This last colloid 

 might probably be purified with advantage upon the dialyser. 



The ammonio-tartrate of iron, ammonio-citrate of iron, and 

 similar pharmaceutical preparations are chiefly colloidal matters. 



Sucrate of Copper. — The deep-blue liquid obtained by adding 

 potash to a mixed solution of chloride of copper and sugar ap- 

 pears to contain a colloidal substance. Placed on a dialyser for 

 four days, the blue liquid became green, and no longer con- 

 tained either potassium or chlorine ; it in fact consisted of oxide 

 of copper united with twice its weight of sugar. The external 

 liquid remained colourless, and gave no indication of copper 

 when tested with sulphuretted hydrogen. The colloidal solu- 

 tion of sucrate of copper was sensitive in the extreme to pec- 

 tizing agents. Salts and acids generally gave a bluish-green 

 precipitate; even acetic acid had that effect. The precipitate, 

 or pectous sucrate, after being well-washed, consisted of oxide 

 of copper with about half its weight of sugar, and is therefore a 

 subsucrate. When the green liquid is heated strongly, it gives 

 a bluish-green precipitate, and does not allow the copper to be 

 readily reduced to the state of suboxide. The subsucrate of 

 copper possesses considerable vivacity of colour, and might be 

 used as a pigment. A solution of sucrate of copper absorbs 

 carbonic acid from the air with great avidity. 



The sucrate of copper dries up into transparent films of an 

 emerald-green colour. These films are not altered in appearance 

 or dissolved in cold or boiling alcohol. In water they are re- 

 solved into sugar and the pectous subsucrate of copper. 



Sucrate of Peroxide of Iron. — The perchloride of iron with an 

 addition of sugar is not precipitated by potash, provided the 

 temperature is not allowed to rise. The peroxide of iron com- 

 bined with the sugar is colloidal, and remains on the dialyser 

 without loss. At a certain stage, however, the sugar appears to 

 leave the peroxide of iron, and a gelatinous subsucrate of iron 

 pectizes. The subsucrate of iron thrown down from the soluble 

 sucrate by the addition of sulphate of potash consisted of about 

 22 parts of sugar to 78 parts of peroxide of iron. 



Sucrate of Peroxide of Uranium. — A similar solution may be 

 obtained by adding potash to a mixture of the nitrate or chloride 

 of uranium with sugar, avoiding heat. The solution is of a deep 

 orange-yellow colour, and on the dialyser soon loses the whole 

 of its acid and alkali. This fluid sucrate has considerable stabi- 

 lity, but is readily pectized by salts, like the sucrate of copper. 

 The subsucrate pectized has considerable solubility in pure water. 



