178 
DE. A. MATTHTESSEN’ OX THE SPECTFIC GEAVITT OE ALLOTS. 
the third determination ; often being re-cast several times, as the castings did not always 
succeed. To prevent as much as possible the formation of internal cavities from crystal- 
lization, the alloys were cast very thin, the thiclcness of the casting being in most cases 
about 3 to 4 millims. 
The method employed for taking the specific gravities, was that of hanging the alloys 
by a very fine platinum wire in distilled water, which had been boiled to free it from 
air, and allowed to cool in mcuo. This method gave better results than that of weigh- 
ing the metal or alloy in a bottle filled with water, on account of the difficulty of per- 
fectly drying the bottle when full, and obtaining the same weight twice following. 
The amalgams which were liquid, and those not sufficiently hard to hang by the pla- 
tinum wire, were weighed in a glass tube to which a platinum wire was soldered. 
The weight of the tube alone in air and water was determined at the temperature at 
which the experiments were made, and therefore, in calculating the specific gravities, 
these values had only to be subtracted from those found. 
The balance used was one of Liebiech’s, which tmns to the OT mgr. when loaded with 
100 grms. in each pan ; and when the alloy was weighed in water, it tmned to the 
0-2 mgr. The air adhering to the alloy, when weighed in water, was removed by a soft 
brush, the alloy being brushed until its weight became constant. 
In calculating the specific gravities, the weight of the water displaced was collected 
for the temperature, so that the unit is in all cases distilled water at 0° C. A similar 
correction could not be made for the temperatmn of the alloys, as theti coefficients of 
expansion are not known. All the weighings were reduced to a vacuum, and a correc- 
tion was made for that part of the platinum -wire which dipped in the water. The 
length of wire dipping in was about 60 millims., which weighed 8 mgrs. these would lose 
in water about O’ 35 mgr. Supposing, as is really the case, that sometimes 10 millims. 
more or less dipped in, the error made would be about 0’06 mgr. ; but as the 0’3 mgr. 
only make an error, if not brought into calculation, in most cases of about O’OOl per cent, 
of the specific gravity found, the error made in this way may be overlooked. 
The equivalents used for calculating the quantities of metal required for the alloys 
were — 
Antimony * . 
.... 122-3 
Silver 
. . . 108 
Tin .... 
.... 58 
Lead .... 
. . . 103-7 
Cadmium . 
.... 56 
Mercury . . . 
. - . 100 
Bismuth . 
.... 208 
Gold .... 
. . . 197 
Table I. gives the 
specific gravities of the pure metals employed, and the temperatm 
(T.) in the Centigrade scale ; the values given are the results of three consecutive deter- 
minations. On account of the number of alloys experimented ufith, it was considered 
as well, in order to save space, only to give the mean of the three determinations ; and 
* Dexter, PoaaEXDOEEF’s ‘ Annaleii,’ vol. c. p. 563. This is the latest determination, and the one 
adopted by Bxjxsen in his recent paper. Liebig’s ‘ Anualen,’ vol. cvi. p. 1. 
