SCIENTIFIC SUMMARY. 
91 
point of silver, and tlie tungstate be extracted from the fused product by 
water, the insoluble portion has the appearance of a crystallised sand, and 
has within a few milligrammes the weight of the silica employed ; that it is 
converted into tridymite is proved by the form and optical characters of the 
crystals. By protracted heating, larger crystals are formed. They have a 
specific gravity of 2 ’30, that of the natural crystals which Yom Rath 
examined, and which contained about 2 per cent, of metallic oxides, being 
2*32, 2*31, and 2-29 . If a heat higher than 1,000° be applied the crystalline 
plates dissolve in the tungstate, and a silicate is formed which floats in the 
melted salt ; while at temperatures less high, at 900° or lower, tridymite 
crystals separate. It is evident that the alkali of the tungstate attacks the 
silica and forms with it an alkaline silicate, tungstic acid being set free ; as 
the temperature falls it again combines with the alkali, and the silicic acid is 
liberated in the crystalline form. The reaction appears to take place at 
lower temperatures than in the case where a phosphate is used. If the fused 
mass already referred to be retained at a lower temperature — nearer, in fact, 
to its melting-point — at about 700°, transparent elongated bodies are formed ; 
if the heating be continued for several hours, double pyramids of quartz are 
noticed which become strongly coloured when viewed between Nicol’s prisms. 
The crystallisation in this case was found to proceed slowly, the action being 
more rapid when the temperature rose and fell frequently between 800° and 
950°. Each time the mass cooled tridymite was formed ; as soon, however, 
as the temperature fell below 850° quartz crystals made their appearance. 
In one instance, where the heating was prolonged for two months, about equal 
quantities of silicic acid had crystallised as quartz and as tridymite. The 
specific gravity of the mixed crystals was 2 ’46, a number intermediate be- 
tween those representing the density of tridymite (2-30) and of quartz (2 , 65). 
In one instance, the greater part of the tridymite was mechanically sepa- 
rated, and here the number rose to 2-61. Analysis showed the crystals to 
contain 0*003 of soda and a mere trace of tungstic acid. — Comptes Rendus , 
1878, vol. lxxxvi. pp. 1133 and 1194. 
Philippium and Decipium. — Delafontaine announces the discovery of two 
metals to which he has given the above names. The former occurs in 
samarskite ; its oxide is yellow, like terbia, and has a molecular weight in- 
termediate between those of yttria and terbia. He has satisfied himself that 
it is not a mixture of those two bodies, and gives the new metal the name 
Philippium in honour of M. Philippe Plantamour, of Geneva. The formiate 
of philippia is less soluble than the corresponding 3alt of yttria, and its 
oxalate is more readily soluble in nitric acid than the corresponding salt of 
terbia. A concentrated solution of a salt of philippium shows a fine absorp- 
tion band in the indigo (A = 450 nearly), two in the green, a faint one in the 
blue, and one in the red. ( Comptes Rendus, 1878, vol. lxxxvii. p. 559.) A 
fortnight after the publication of this note, Delafontaine announced {Ibid. 
p. 632), the discovery of a second metal in the samarskite of N. Carolina, 
and this he has named Decipium. It forms an oxide, the equivalent of which 
is close upon 122 for the formula DpO (or Dp 2 0 3 = 366). The acetate is less 
soluble than that of didymium, and more so than that of terbium ; the 
decipio-potassium sulphate is only slightly soluble in a concentrated solu- 
tion of potassium sulphate, but easily soluble in water. The absorption 
