320 C H E M I 
ayailed himfeff of its oxyd as an improvement in enamel 
painting ; and leaves of platina are advantageoufly ufed 
for plating China-ware, or porcelain. 
Two parts of platina, accurately mixed with one of 
arfenic and tartar, when expofed to a glow heat in a luted 
crucible, melt into a brittle fubilance, ftill whiter than 
platina. This lubltance is eafily foftened by the fire, or, 
by a ffror.ger heat, completely melted. In this date, if 
expofed for a fufficient length of time to the fire, the 
arienic is difiipated, and the platina, which again be¬ 
comes folid, alone remains. Achard has recently taken 
advantage of this property, to form vefiels of all forts 
from platina, a liibllance lo infufible by itfelf; a circum- 
itance which feems to lead to further improvements, of 
infinite importance to fociety. 
OF VEGETABLE SUBSTANCES. 
In our enquiries into vegetable fubftances, we have to 
confider, firlt, the living vegetable, its functions, its pro¬ 
ducts; next, the dead vegetable, and the alterations it 
undergoes. Next to thefe, we are to examine the gene¬ 
ral principles and organization of vegetables, and then 
pafs to the fubltances that contribute to their develope- 
ment, their nourifhment; and the circumftances that 
may forward or retard their growth ; all of which natu¬ 
rally leads to obfervations on the manuring and fertilis¬ 
ing different foils; the theory of compofts, watering, 
marling, and ploughing land; and improving hence the 
fcience of Husbandry. 
Nature prefents us with three claffes or orders of being, 
very different and diftinct from each other; namely, mine- 
als,vegetables, and animals. The grand charaCteriftic of 
organized fubftances, is their perpetual change of form, 
of nature, of place, &c. The diftinguilhing character 
of vegetables and minerals, is, that by the aid of heat 
the firft yield carbon, which the latter do not ; another 
diltinCtion is, that the'firft are homogeneous, the others 
compofed of various fubftances. 
Vegetables are formed of fix parts, or organs, deftined 
to perform peculiar functions, the products of which are 
made known by vegetable analyfis. Thefe parts are the 
root, the Item, the leaf, the flower, the fruit, and the 
feed. Thefediffer in form, texture, magnitude, number, 
colour, duration, tafte, &c. for particulars of all which 
fee Botany, vol. iii. p. 234-, and leq. 
Vegetable analyfis is very different now, from what it 
was fame years ago. The ancient chemifts laboured 
continuadly in the diftillation of vegetable matters, which 
always gave nearly the fame refults. But this method is 
now almoft laid alide, to bring forward the analyfis by 
menftrua, or folvents. Boulduc, Geoffrey, and others, 
worked largely in this way, and hence diftinguifhed the 
mucus of refins, and threw conuderable light on this part 
of chemiftry. But the dilcovery of elaftic fluids, about 
the years 1770 and 1772, railed vegetable enquiry to a 
much higher degree of perfection. We are indebted to 
Fourcroy for a clear methodical work upon thisfubjeCt. 
Ke delcribes eight fpecies of analyfis, very diftinCt from 
each other. 1. Natural analyfis; as when the vefiels are 
choaked up, and burft; and there is a flowing out of 
lap, gum, fugar, or refin. The flip runs commonly in 
the fpring ; and, befides thefe fubftances, vegetables alfo 
furnilh eroma, and water. 2. Artificial immediate ana¬ 
lyfis : In this we aflift nature ; as, when a plant feems 
ready to let fome matter efcape, the ftjiflars are applied 
to make it run freely: this is done to obtain refins, 
manna, faccharine liquors, &c. 3. Immediate artificial 
analyfis upon dead vagetables ; as by expreflion, to pro¬ 
cure linfeed oil, fixed oils, &rc. 4. By fire: Vegetable 
matters fometimes require a gentle heat; vegetables 
tranlported from the north to the fouth dry up, and 
change their colour, and even their fpecific weight: this 
is called defecation ; it is however a beginning of decom- 
-S T R Y, 
pofition, Vegetables may be expofed to a heat of 45 0 ; m 
that cafe, the defecation is quicker, and the decompo- 
tion is already apparent; with a ftrongerheat the vege¬ 
table matters are entirely decompofed: then they give 
out phlegm, black oils of different weights, carbonic 
acid, carbonated hydrogen, pyromucous acid, and often 
a pyromucite of ammoniac and carbon remain in the 
retort. This manner of analyfing gives all that was con¬ 
tained in the vegetable, but the conftituent matters are 
combined in a different order, and in general the products 
are more fimple : thus, by analyfing a quaternary com¬ 
bination, we often have ternary and binary ones; and 
the produdls are generally mineral matters, as water, 
carbonic acid, hydrogen gas, and carbon. 5. By wa¬ 
ter : If by cold water, it is maceration ; if warm wa¬ 
ter, infuflon ; if boiling water, decodlion ; but water 
at different degrees of heat gives very different re- 
lults. There is a fourth way of ufing water; which is to 
leave the vegetable a long time in foak, as when wood is 
carbonated by water: this is called analyfis by the flow and 
long-continued aft ion of water. 6. Analyfis by acids, and 
by falts in general. It is not to be wondered at that ana¬ 
lyfis fliould be now better underftood, fince we know fo 
well the cornpofiticn of the folvents we ule. There are 
acids which will only diffolve vegetable matters, as vine¬ 
gar; while others are decompofed over them, and reduce 
them entirely to water and to carbonic acid. The adtion 
of acids upon vegetables is fuciv, that the chemift, by 
varying their proportions, can produce, at his pleafure, 
either tartarous acid, malic acid, oxalic acid, or acet¬ 
ous acid : this arifes from the bafe of all the vegetable 
acids being at leaft binary; carbon and hydrogen, the 
bafe, combined with different proportions of oxygen, 
produce the acids we have mentioned. Neutral falts are 
principally the prefervers of vegetables; but alkalis 
often deftroy them entirely. 7. By fermentation. Thus 
infipid matters become fweet, then fpirituous: fuch is 
the art of the brewer, and maker of wine. There are 
three kinds of fermentation, the fpirituous , the acetous , 
and the putrid. 8. Analyfis of vegetables, by the pro- 
dudts of vegetables ; as iA decompoling a vegetable fub- 
ftance by vegetable acids, oils, alcohol, or ether. This 
laft analyfis is the molt complicated and difficult'. 
In the analyiis of vegetables, the moll fimple mode 
here laid down fhould be firft ufed. Then treat the pro¬ 
ducts obtained from this firft analyfis by all the other 
modes ; and the analyfis is complete. The firft and fe- 
cond mode of analyfis procure immediately, and without 
alteration, the fap, juices. See. 
Of the SAP. 
It is now generally underftood that the fap is the pri¬ 
mary fource of the various nutritive juices, which adt 
in the growth of vegetables, and the formation of their 
parts. Deyeux has a Memoir on this fubjedt in the Jour¬ 
nal de Pharmacie. He concludes from his own refearches 
and analyfis, 1. That the fap which appears at the be- 
gining of the vegetation, and which flows, whether fpon 
taneoufly or by incifion from the yoke-elm and the vine, 
is a compound liquor. 2. That it contains calcareous 
earth united with acetous acid. 3. That it holds in 
folution, by means of the fame acid, a vegeto-animal 
fubltance or matter. Vauquelin has alfo lately examined 
different kinds of ftp, as, of the common elm, the beech, 
the birch, and the yoke-elm. In all thefe, he ccnftant- 
ly found acetit of potafii and acetit of lime; in the elm, 
the acetit of potafh was almoll pure, forming very near 
•9 of the refidue by evaporation ; he found carbonat of 
lime alfo. The fap of the birch contains, befides the 
acetits of potafii and lime, an excefs of acetous acid, 
and fucli a plenty of faccharine matter, as to be fufcep- 
tible of the vinous fermentation, and to afford alcohol. 
In the fap of the beach Vauquelin found a pretty large 
quantity 
