

TRANSACTIONS OF THE SECTIONS. 27 
Sulphate of oxide of lanthanium crystallizes in small six-sided prisms terminated by 
six-sided pyramids, containing three atoms of water of crystallization. This salt has 
the same property as sulphate of yttria, thorina, and other oxides of the same class, 
namely, being much less soluble in warm than in cold water. At 73°4 Fahr. one 
patt of anhydrous sulphate of oxide of lanthanium requires 423 parts of water to 
be dissolved, but of boiling water one part of the same salt requires about 115 parts. 
The crystals are very slowly dissolved, but the anhydrous salt is immediately dis- 
solved. The anhydrous salt developes much heat when mixed with a little cold 
water, and the salt then forms a crystalline crust, which afterwards is very slowly 
dissolved. If powdered sulphate of oxide of lanthanium be thrown into water whose 
temperature is 35°6 or 37°4 Fahr., and kept stirring, and with the precaution that 
the liquid, which besides should be cooled from the outside, never attains a higher 
temperature than 55°'4 Fahr., one part of sulphate of oxide of lanthanium may be 
dissolved in less than six parts of water, and the solution preserved unchanged for 
weeks, in closed vessels, and within the stated limits of temperature ; but if the liquid 
be gradually heated, then before the temperature has reached 86° Fahr., a number 
of crystalline groups composed of small needles radiating from a common centre 
begin to deposit, and when once this crystallization has commenced it cannot be 
checked, however rapidly we may cool the liquid. With regard to the number and 
form of the deposited groups, the originally clear liquid is changed in a few minutes 
toathin pap. If during the dissolution of the salt according to the manner stated, 
a part of the liquid acquires a higher temperature through the heat that is developed 
by the union of the salt with water, the crystallization of a part of the salt immedi- 
ately begins, and after that has once begun the phenomenon continues even with so 
low a decree of heat as 55°4 to 57°2 Fahr. less, until the solution only contains 
¢yths of its weight of anhydrous salt. The salt which has thus been deposited con- 
tains the same quantity of water as that which is formed during the evaporation, as 
well under 55°4 Fahr. as with 212° Fahr. If sulphate of oxide of lanthanium be 
kept at a white heat for an hour, it loses the half of its sulphuric acid, and the basic 
salt which is produced is insoluble in water. 
Nitrate of oxide of lanthanium is a salt easily soluble in water or alcohol, and from 
an evaporated solution of the consistence of thin syrup, it crystallizes in large pris- 
matic crystals, which rapidly deliquesce in damp air. If the solution be evaporated 
with a heat of 86° Fahr. and above, an opake milk-white mass is obtained. If the 
salt be cautiously heated so that all the water is expelled, then by care with a higher 
degree of temperature, the anhydrous salt may be melted without decomposition, 
and after cooling it resembles a colourless glass ; but with the least inattention re- 
specting the temperature, a part of the nitric acid is expelled, and the melted mass 
is a mixture of neutral and basic salt, which stiffens to a snow-white opake mass, 
which a moment after solidification has the remarkable quality of falling asunder into 
a voluminous white powder, with such violence, accompanied by a sort of slight 
detonation, that parts of it are thrown about to the distance of several inches, 
- Oxide of lanthanium has a particular tendency to form basic salts, and only such 
are precipitated with caustic ammonia, let this be added in as great an excess as 
may be, when also it occurs that the combination with some organic acids, such as 
tartaric acid, is dissolved in an excess of ammonia. Several of the basic salts, for 
example, basic nitrate of oxide of lanthanium, and basic chloride of lanthanium, are 
marked by the quality that they cannot be washed upon a filter with water, which 
runs through of a milky colour, until no part of the precipitate remains upon the 
filter, and if the liquid be boiled with the precipitate which has been obtained, the 
whole runs immediately through the filter. If the precipitate be allowed to remain 
a few days wet upon the filter, it becomes changed into a neutral salt which is dis- 
solved in the water, and carbonate of oxide of lanthanium, which remains upon the 
filter. 
~ With regard to cerium, my investigations are as imperfect in their results as those 
upon lanthanium ; I will, however, make mention of some facts which may prove 
interesting for the present. 
The reddish-brown powder which remains after the extraction of oxide of lantha- 
nium with dilute nitric acid, is a mixture of the oxide of cerium with oxide of lantha- 
