418 
DR. A. W. HOKMAA^^ OX THE PHOSPHOEES-BASES. 
grouped round [1 0 0], as in Fig. 9. It is found sometimes that several crystals, like 
those of Fig. 8 , are associated by 0 0 1. 
It deserves to be noticed that the crystals (Figs. 2, 3, 4, 5 and 7) were fonned in the 
presence of hydrochloric acid, and that in the absence of this acid, only crystals of 
Fig. 8 are obtained, which, without the study of the cleavage and the optical charac- 
ters, could not be distinguished from trimetric crystals. 
Cleavages 0 01 and 110 distinct and easily obtained. The cleavage 1 1 0 of the 
hemitropic crystals (Fig. 8 ) exhibits re-entering angles. 
Lustre vitreous on the fracture, fatty on the faces. 
Hardness someAvhat greater than that of gypsum. 
The crystals are optically positive ; the line of symmetiT [0 1 0] is then* principal 
medium line. The coloured rings are risible through the faces of the cleavage 110, 
and the plane of the optical axes appears to be perpendicular to the axis of the 
prism 110. Through the cleavage 1 1 0 of the hemitropic crystals (Fig. 7), two systems 
of rings are seen. 
The angle of the optical axes, seen through the faces 110 and 1 1 0, is 7 4°. By rough 
measurement through 0 01 and 011 , the value of the smallest index of refraction 
y=l'58 was determined approximately; and since the apparent optical axes deriate 
only by a few degrees from lines normal to 1 1 0 and 110 , the conclusion is admissible 
fhat the internal angle of the optical axes differs but little from 78”*.” 
Oxide of Triethi/l2)hos])]iine and Bichloride of Platinum. 
No precipitate is formed on mixing the aqueous solutions of the two compounds, how- 
ever concentrated ; but on adding the anhydrous oxide to a concentrated solution of 
dichloride of platinum in absolute alcohol, a crystalline platinum-compound is deposited 
after a few moments. This compound is exceedingly soluble in water, easily soluble in 
alcohol, insoluble in ether. On addmg ether to the alcoholic solution, the salt is preci- 
pitated, although with difficulty, in the crystalline state. The alcoholic solution, Avhen 
evaporating spontaneously, yields beautiful hexagonal plates, frequently of rather large 
dimensions. On account of its extreme solubility, it is not quite easy to obtain this salt 
in considerable quantity. 
Analysis has led to the someAAdiat complicated formula 
C 24 Hgo P 4 O 3 Pt 2 Cl, = 3[(C, H,) 3 F O], (C 3 li,), P CL, 2Pt CL. 
I. 0-4187 grin, of the platinum-salt gave 0-4632 grin, of carbonic acid, and 0-2545 
grin, of Avater. 
II. 0-5185 grin, of the platinum-salt, precipitated Avith sulphuretted hydrogeii, &c., 
gave 0-1092 grin, of platinum, and 0-4808 grin, of chloride of silver. 
* Some of Sella’ s ci-ystallograpliical researches were received whilst this paper was passing through the 
press. These researches will be published iu detail in Jlemorie della Beale Accademia delle Scie?ize di 
Torino, Serio 2. tom. xx. under the title; Sidle Forme Cristalline di alcuni Sali derivati dalV Am moniaca 
per Quintixo Sella, Depidato al Parlamento Italiano. 
