lilE. T. GEAHAM ON LIQUID DIFFUSION APPLIED TO ANALYSIS. 
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The siicrate 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 resolved 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 per- 
oxide of iron combined 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 poetizes. 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 solu- 
tion 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 stability, but is readily pectized by 
salts, like the sucrate of copper. The subsucrate pectized has considerable solubility in 
pure water. 
Sucrate of Lime. — The well-known solution of lime in sugar forms a solid coagulum 
when heated. It is probably, at a high temperature, entirely colloidal. The solution 
obtained on cooling passes through the septum, but requires a much longer time than 
a true crystalloid like the chloride of calcium. 
The blue solution of tartrate of copper in caustic potash contains a colloidal com- 
pound, which has not been fully examined. 
Soluble Chromic Oxide. — The definite terchloride of chromium, being a crystalloid, 
difiuses away entirely when placed in solution upon the dialyser. This salt dissolves, 
with time, a certain portion of freshly-precipitated hydrated chromic oxide, and becomes 
of a deeper green colour. Such a solution, after dialysis for twenty-two days, contained 
8 hydrochloric acid to 92 chromic oxide; and after thirty days, 4’3 acid to 95 ’7 oxidCj 
or I equiv. acid to 10-6 equivs. oxide. After thirty-eight days, the solution gelatinized 
in part upon the dialyser, and then contained 1‘5 acid to 98'5 oxide, or 1 equiv. acid to 
31 '2 equivs. chromic oxide. This last solution, which may be taken to represent soluble 
chromic oxide, is of a dark green colour, and admits of being heated, and also of being 
diluted with pure water without change. It was gelatinized with the usual facility by 
traces of salts and other reagents which affect colloid solutions, and was then no longer 
soluble in water, even with the assistance of heat. It appeared to be the green hydrated 
oxide of chromium, as that substance is usually known. A metachromic oxide may 
possibly be obtained by heating and dialysing the acetate, but I have not attempted to 
form it. 
]Mr. Okdway succeeded in dissolving an excess of the hydrated uranic oxide and 
of glucina in the chloride of uranium and of glucinum respectively. The dialysis of 
such solutions may be reasonably expected to yield soluble uranic oxide and soluble 
glucina. 
It appears, then, that the hydrated peroxides of the aluminous type, when free, are 
