Interefting Chemical News. 
ere, to get rid of which, he fluxed in 2 
filver crucible, a quantity of tin ore with 
fix parts of pot-ath. Of this mixture he 
found that 0.91 were foluble in water, and 
capable of being precipitated and re-dif- 
. folved by muriatic acid. By decompofing 
the muriate of tin by carbonate of foda, 
he acquired an oxide. very foluble in 
muriatic acid, and which, when preci- 
pitated by zinc and heated in a crucible 
with fat, gave a button of pure metallic 
tin. According to KLAPROTH, therefore, 
the caule of the infolubility of tin ore in 
muriatic¢ acid, is owing to its being fuper- 
faturated with oxygen; it does not ap- 
pear, however, that fufion with pot-ath 
at all tended to de-oxidate it; for in 
order that the mixture of tin ore and pot- 
afh fhould be foluble in water, it is necef- 
fary that the firft fhould be in the extreme 
ftate of oxidation ; in other words, in the 
ftate of acid. To put the matter, how- 
ever, beyond all doubt, a portion of tin 
was diffolved in nitric acid, evaporated 
to dryneis, and repeatedly treated in the 
fame manner with frefh acid; being thus 
fuperfaturated with oxygen, and wathed 
well in diftilled water, it was thrown 
into muriatic acid, and perfeCtly diffolved. 
It is probable, therefore, that the great 
degree of aggregation between the parts 
of the ore, and which fimple pulverization 
could not overcome, was the true caufe 
of its infolubility in muriatic acid, and 
that the action of the pot-afh was fimply 
the overcoming of this aggregation. 
In the fame valuable number we find . 
an eflay by M. De Saussure, jun. on 
the queftion, ** Is the formation of 
carbonic acid effential to vegetation?” 
From feveral ingenious experiments en 
vegetation in atmofpheric air, mixed with 
different. proportions of carbonic acid, 
and in atmofpheric air deprived of car- 
bonic acid, Mr. De S. has deduced the 
* following laws : 
1. That plants, like animals, are 
eontinually forming carbonic acid while 
yegetating, either in the light or fhade. 
2. That like animais, they form this 
carbonic acid, by means of the oxygen of 
the atmofphere; and that the reafon why 
the formation of this acid is not al- 
ways manifeft, is its being immediately 
decompofed. 
3. That the prefence, or rather the 
elaboration of carbonic acid, is neceflary 
to vegetation in the light. 
4. That hght is favourable to vegeta- 
tion, by ‘contributing to the cecompofi- 
tion of carbonic acid, 
.digeition 77.5 grs. of filex. 
293 
5. That plants, while vegetating in 
the light, can fupport a dofe of carbonic 
acid fo ftrong as to deftroy them when in 
the fhade. 
The following analyfis of the pumice- 
{tone of Lipari, is tranflated into the 
fame work trom the German of KLAP- 
ROTH, by Cit. TassarEtT, with notes 
by GuyTon. The pumice-ftone is con- 
fidered by Bergman, Cartheufer, and Spal- 
lanzani, on account of its fibrous ftruc- 
ture, and the magnefia which it was fup- 
pofed to contain, as an afbeftos altered by 
volcanic fire: to determine this, the fol- 
lowing analyfis was inftituted : 
The greyifh white fibrous pumice of 
Lipari, which floats on water, was pul- 
verized and boiled for fome time in water: 
no portion of it, however, appeared to 
be diffolved; the water difcovered, in- 
deed, on the addition of nitrate of filver, 
a flight trace of muriatic acid. _ 
One hundred grs. of this ftone reduced 
to powder, were mixed with twice their 
weight of pot-afh and fufed: the mais 
appeared of a green colour, fhewing the 
prefence of a little oxide of manganefe: 
when diffolved in water, it formed a 
brownifh liquor; this being faturated 
with weak muriatic acid, depofited on 
A itecond 
precipitate being the whole of what was 
contained in the liquor, was obtained, 
by the addition of ammoniac: this pre- 
cipitate being digefted in 2 hot folution of 
pure pot-afh, re-diffolved the whole ex- 
cept 1.75 grs. of oxide of iron. The 
alcaline liquor, containing alumine, was 
“fuperfaturated by muriatic acid, and the 
alumine precipitated by carbonate of pot- 
afh ; when wafhed and dryed, it weighed 
17.5 grs. It was evidently pure alu- 
mine; for being re-diflolved in fuiphuric 
acid, with the addition of acetile of pot- 
ath, it gave cryftals of alum. The com-. 
ponent parts, therefore, of the pumice of 
Lipari are | 
Silex 77.50 
Alumine 17.50 
Oxide of iron 1.75 
Afmall trace of manganefe 
| 96.75 
The acids have no action on the fimple 
pulverized | ftone,° except abfiracting ‘the 
manganefe, which inertneis arifes fron 
the force of the aggregation of its con- 
ftituent parts. Though the pumice is 
{fo light as to float on water, yet when 

reduced to a moderately fine powder,. its. - 
fpecif,' grav. is 2.142, or about equal to 
that of the opal or pitchitone. 
| NEW 
