114 
NMALORLE 
[| Mov. 25, 1869 
two spectra are formed, one from blood on the stage of the 
microscope, and the other from the same on the stage of the eye- 
iece. 
3 The dark band of the chlorophyll spectrum is slightly variable 
in width—and the action of acids and alkalies sometimes causes 
a slight displacement, the former raising (moving toward the blue 
end) and the latter depressing. The endochrome of a diatom 
after treatment with acid is green, and the acid, in this case, 
produces scarcely any displacement of the band, which may be 
observed even in the dark reddish mass of the dead Diatomacez, 
almost identical in colour with the ferrous carbonate so often 
found in bogs where the larger diatoms are abundant ; and what 
is more remarkable is, that the carbonate gives no absorption 
bands at all. As a general rule, alcoholic solutions of chlorophyll 
and diatomin have the band slightly depressed, reading I to 14 
on the interference scale.—[Amer, Jour. Sci. and Arts. ] 
CHEMISTRY 
Thallium Salts.—I. 
MM. Lamy AND Des CLOISEAUX have resumed the study ot 
the principal thallium salts, with the view of ascertaining their 
chemical ;composition, optical properties, and crystalline form 
(Annales de Chimie et de Physique, xvii. 310). The method of 
obtaining crystals was that which M. Deville has 'for a consider- 
able time been in the habit of employing in his laboratory. A 
given substance is placed in contact with water, or some other 
solvent, either in a closed or lightly covered vessel, and exposed 
to the usual conditions of temperature of an inhabited apartment ; 
if these do not suffice, the liquid is heated every day for an hour 
to a certain extent. In course of time, even the most micro- 
scopic crystals, if submitted to this process, become large, 
well-formed, and transparent. 
The thallium in these salts was determined as iodide ; a com- 
pound which from its sparing solubility (especially in water con- 
taining a little potassic iodide), as well as on account of its great 
specific gravity and crystalline character, is very well adapted to the 
purpose. The density of thallous sw/phate, T12SO,, is 6°603,* 
and its form a right rhomboidal prism, geometrically and 
optically isomorphous with ammonic sulphate. ‘The crystals 
often appear unsymmetrical, on account of the unequal develop- 
ment of the different faces. The optic axes are wide apart; 
and the dispersion of the axes, as observed in oil, is feeble, with 
p<v. To the already known{thallium a/wms may be added a 
mixed series, having the general formula : 
(Al, 0, . Fe;03)3SO03 + (K,0. T1,0)SO, + 24Aq. 
Special attention is directed to one of these, which was 
obtained accidentally in the course of a lixiviation, and had the 
formula : 
[(Al,03)3(Fe,03)313SO3 + [(K,O)$ (T1,0)t] SO; + 24Aq. 
Its colour is slightly yellow, and in solubility it much resembles 
potassic alum. After several solutions and recrystallisations, the 
whole of the iron is removed, and the following alum appears : 
Al,O, . 3803 +[(K,O)2(T10)4] SO, + 24Aq. 
Zinco-thallous sulphate— 
T1,SO,+ ZnSO, +6H,0, 
which had already been described by Willm and Werther, 
belongs to the oblique rhomboidal prismatic system, and is 
geometrically isomorphous with ammonio-ferrous sulphate, 
potassic magnesio-sulphate &c. (as, indeed, Werther has shown) ; 
but it is optically different from these salts, both in orientation and 
in the sign of its acute bisectrix (negative), 
Plane angle of the base ....... 
Plane angle of the lateral faces... . 
Obliquity of the primitive prisms . . 
The optic axes lie in the plane of symmetry. There is a strong 
proper dispersion with p<yv. The zzclined dispersion is weak, 
and only brought out by a difference in the brightness of the 
colours lying at the edges of the hyperbole of the two systems of 
rings. Thallous #7tvate, TINOs, has the specific gravity 5°550, 
and occurs in right rhomboidal prisms of 125° 52’ (the corre- 
sponding angle for nitreis 118° 50’). The plane of the optic axes 
is perpendicular to the corresponding plane in potassic nitrate. 
The acute bisectrix is negative, and the dispersion of the axes 
considerable, with p< ». This salt had been already examined 
optically by Miller. In order to prepare thallous carbonate, 
107° 5 14” 
99° 31’ 24” 
106° 10! 00” 
* The temperature in this and following determinations is not given in the 
memoir. 
(T1,CO,), a saturated solution of thallous oxide in alcohol was 
exposed to air, in contact with a lamina of thallium. At the end 
of six months, very large crystals were obtained. ‘These have 
an adamantine lustre, and a specific gravity 7°164; they 
belong to the clino-rhombic system, thus agreeing neither with 
plumbie, potassic, nor ammonic carbonate. Macles by hemi- 
tropy round one particular axis, are frequently observed. The 
plane of the optic axes is normal to the plane of symmetry, and 
almost exactly perpendicular to the base. The acute bisectrix 
is negative, and normal to the horizontal diagonal of the base ; 
the double refraction energetic. The dispersion of the optic 
axes is well marked, with p < v; while the Aorizonfal dispersion 
is, on the contrary, inappreciable. An attempt to prepare other 
thallous carbonates did not succeed. 
Di-thallous phosphate— 
2[T],HPO,]. H,O, 
is a very soluble salt, anhydrous at 200°, and crystallises in the 
rhombic system. Lustre vitreous. The dispersion of the optic 
axes is strong, with p> v. AZono-thallous phosphate— 
TIH,PO,, 
is very soluble in water, and readily crystallises in long volumi- 
nous needles which were submitted to the growing process 
already described. Density 4°723. The crystals may be 
referred to a clino-rhombic prism of 34° 59’. having a base 
only slightly sloping towards the lateral faces. Macles by 
hemitropy are common, giving rise to a re-entering angle of 
176° 32’. The plane of the optic axes is parallel to the horizontal 
diagonal of the base. Acute bisectrix negative ; horizontal dis- 
persion indistinct ; proper axial dispersion considerable. The 
pyrophosphate— T1,P..0,, 
crystallises in magnificent transparent prisms, soluble in water 
with partial decomposition, softened by a heat of 120°, and 
having the density 6°786. Its form is an oblique rhomboidal 
prism. The crystals are fragile, and have a somewhat adaman- 
tine lustre. The plane of the optic axes is normal to that of 
symmetry, and almost parallel tothe base. While the horizontal 
dispersion is but slight, the proper dispersion of the axes is the 
greatest hitherto observed, as shown by the following means of 
measurements taken in oil and air, determining the apparent 
separation of the axes in air at 24°: 
2E=125° 48’ (red rays) ; 112° 30’ (yellow); 
2E=89° 47’ (green rays) ; 52° 34’ (blue). 
The Aydrous pyrophosphate— 
T1,P,0, + 2H,0, 
separates from the mother-liquid of its predecessor. It is soluble 
in water with but little decomposition ; but it is less stable at 
a high temperature than the anhydrous salt, which, on the 
other hand, it exceeds in the intensity of its vitreous lustre, its 
hardness and cohesion. ‘The plane of the optic axes is normal 
to the plane of symmetry: the acute bisectrix negative and per- 
pendicular to the horizontal diagonal of the base. Horizontal 
dispersion feeble ; proper dispersion of the axes considerable, 
with p<v. The ammoniacal thallous phosphate— 
3NH,. H3PO, + 2NH,;. H, TIPO, 
is obtained by adding ammonia to the common phosphate, 
filtering to remove tri-thallous phosphate, and evaporating the 
mother-liquid. The crystals are very soluble in water, and 
completely isomorphous with ammonic phosphate. ‘Their figure 
is that of a right prism with square base, elongated in the 
direction of the vertical axis, and terminated by an octohedron 
of 119° 50’. The double refraction is on a negative axis. 
E. J. M: 
PHYSICS 
Pfaundler on the Regelation of Ice 
THE fact observed by Faraday that two pieces of ice freeze 
together when brought into contact has met with various explana- 
tions. Helmholtz, for example, assumes that pressure is always 
at work in regelation; hence depression of the fusion point 
of the ice, and a cold sufficient to freeze a small portion of water 
in another part of the mass. Tyndall, on the other hand, admits 
the hypothesis of pressure only where it is actually observable ; 
but, in other cases, explains the phenomena by a difference 
between the fusion-point inside and at the surface of the ice. 
Schultz has actually verified Tyndall’s theory with water from 
which the air had been expelled. 
