352 On the Purification of Mercury. 
phuretted hydrogen gas, which is net only sensible to the smell, 
but is proved by the test of paper moistened in a solution of ace- 
tate of lead ; from which it appears that, besides the sulphurie 
acid being decomposed, the water with which it was united is 
also at the same time decomposed. 
_ Lastly. By the same means I have separated mercury from 
the amalgam of mirrors*. : 
This experiment, which is pleasing in theory and principle, 
may even serve to demonstrate in the shortest period of time 
that, from sulphuric acid, sulphur may be extracted, In fact, 
putting in a two-ounce phial, for example, a quarter of an ounce 
(six denari) of the said amalgam, and adding concentrated sul- 
phuric acid sufficient to cover it from one to two inches deep, 
and aiding the operation by shaking the bottle, that all the amal- 
gam may mix with the acid, after a few minutes, particularly 
when the temperature of the atmosphere is not low, a most vivid 
ebullition takes place, accompanied by copious vapours, by the 
disengagement of much. caloric, of sulphurous acid, .of sul- 
phuretted hydrogen gas, and also of sulphur. The last remains 
attached to the neck of the bottle, and in the greater quantity 
the less the mouth of the bottle may be. Separating the resi- 
due, which is more or less whitish, by washing, the amalgam 
contained much less tin than at first; and submitting it agam 
many 
* Van Engestrom to obtain the mercury from this amalgam proposed to 
distil it with powdered charcoal or with sulphur. Ann. de Chimie, xxvi, 293. 
[Note by the Translatcr.]| Another experimental proof of the purity of the 
mercury thus refined, is the excellence of the thermometers made with it 
by the enlightened author's assistant}, with one of which I was presented 
at Pisa, and which | found exactly corresponding to a very good one made 
inLondon. In all the experiments which [ have made with these two ther- 
mometers, I have not been able to discover, even with a magnifying glass, 
the least difference in their sensibility. Whether in the open air of the 
plains, on the Pisz mountains, in the vale of the Arno, the imsalubrious fur- 
nace (in winter perkaps it may be called basin) of Florence, the heights of 
Feisole, the Apennines, the Pisa baths which are at the spring 100°, at that 
of Jove 94, and that of Ceres 93, or the baths of Lucca, which at the spring 
within the cave are 130°.76, at the hothath 1262 ,&c.—the rise or fall of the 
‘mercury in both instruments was identically the same. The day on which 
I examined the Lucca baths, when the thermometers were exposed to the 
direct rays of the sun at the foot of the hill beneath the baths, and on the 
sheltered bank of the riyer, they rose in a very few minutes to 116°, and 
would have risen still higher had they, been allowed more time. Both the 
Lucca and Pisa hot waters, like those of Bath, contain very little extraneous 
matter, much lessthan might be inferred from their high temperature and their 
respective situations near the base of lofty ridges of calcareous mountains : 
some depositions or incrustations of carbonate of lime appear at their source, 
but they contain very little gas and noiron. Dr. Franceschi, physician at the 
Lucca 
iys Cela’ bie i 
+ In Savoy, Piedmont, and even Tuscany, persons who make barometers 
and thermometers are wholly unknown. : 
= ae 
