C A O CAP 745 
parts of the caoutchouc are drawn nearer each other by does not appear that we have any thing to fear in practice 
the evaporation of the interpofed bodies. The great affi- from a combination between thefe two bodies, which, 
nity between thefe two bodies is feen by the length of time though it really is a true folution, does not take place in 
that the odour of the ether remains, notvvithftanding the any fenfible degree but at a high temperature. It is there- 
great volatility of the latter, and that the apparent dry- fore at prefent eafy to make of caoutchouc whatever in- 
nefs of the tube feems to fhew that there is none remain- ftruments it may be advantageous to have of a flexible. 
in ; ; neverthelefs, after a certain time, the odour difap- 
pears entirely. 
“ Although the procefs 1 have been defcribing is but 
very little expenlive, yet I have tried to employ other fol- 
vents in lieu of ether, becaufe it is not to be had in every 
place, and requires particular care in its prefervation. I 
have employed, with fome fuccefs, the eflential oils of la¬ 
vender and of turpentine : both of them fpeedily dilate 
the caoutchouc, and are of no great price. The difagree- 
able fmell of 'he oil of turpentine becomes, perhaps, in pro¬ 
cefs of time, lefs difagreeable than that of lavender. This 
laft is dearer ; but the difference is not fo great as it ap¬ 
pears at firft : for we may make fome advantage of the oil 
of lavender that is employed by the following operation : 
upon plunging into alcohol the elallic tube prepared with 
the oil of lavender, the alcohol charges itfelf with the oil, 
and forms a very good lavender-water ; the fame as would 
be made by an immediate mixture of oil of lavender with 
fpirit of wine, lmmerlion in this liquor alfo ferves to 
haften the drying of the caoutchouc inflruments thus made 
by means of eflential oils. I have made tubes with the oils 
of turpentine and of lavender ; both are much flower in 
evaporating than ether. The oil of turpentine particular¬ 
ly appeared to me always to have a kind of ftickinefs, and I 
know not as yet that we have any means whereby to get fpee¬ 
dily rid of its fmell. Neverthelefs there is a folvent which 
has not that inconvenience ; it is cheaper, and may ealily 
be procured by every one : this folvent is water. I con¬ 
ceive it will appear ftrange to mention water as a folvent 
of elaftic gum, that liquid having been always fuppofed 
to have no adtion upon it. 1 myfelf refilled the idea ; but 
reflecting that ether, by being faturated with water, is the 
better enabled to adt on caoutchouc, and that this gum 
when plunged into boiling-water becomes more tranfpa- 
rent at the edges, I prefumed that this eft'edt was not due 
Amply to the dilatation of its volume by the heat. I thought 
that, at that temperature, fome adtion might take place, 
and that a long-continued ebullition might produce more 
fenfible effedts. I was not difappointed in my expectations, 
and one of thofe tubes was prepared without any other 
folvent than water and heat. I proceeded in the fame 
manner as with ether : the-elaftic gum dilates but very 
little in boiling water ; it becomes whitifli, but recovers 
its colour again by drying it in the air and light. It is fuf- 
nciently prepared for ufe when it has been a quarter of an 
hour in boiling water : by this time its edges are fome- 
times tranfparent. It is to be turned fpirally round the 
mould, in the manner we defcribed before, and replunged 
frequently intothe boiling water, during the time that is em¬ 
ployed in forming the tube, to the end that the edges may 
be difpofed tb unite together. When the whole is bound 
with packthread, it is to be kept fome hours in boiling 
water; after which it is to be dried, ftill keeping on the 
binding. If we wifli to be more certain that the connec¬ 
tion is perfedl, the fpiral may be doubled ; but we mu ft 
always avoid placing the exterior furfaces of the flips one 
upon the other, as thofe furfaces are the parts which molt 
refill the adtion of folvents. This precaution is lefs necef- 
fary when ether is employed, on account of its great ac¬ 
tion upon the caoutchouc. 
“ It might be feared that the adtion of water upon ca¬ 
outchouc would deprive us of the advantages which might 
otherwife be expelled ; but thefe fears will be removed, 
if we confider that.the affinities differ according to the tem¬ 
peratures ; that it is only at a very high temperature that 
water exercifes any fenfible adtion upon caoutchouc. I 
Can affirm, that at 120 degrees of Reaumur’s thermometer- 
(302 degrees of Fahrenheit) this affinity is not fuchasthat 
the water can give a liquid form to caoutchouc; and it 
Voii.III. No. 159. 
fupple, and elaftic, fubltance, which is impermeable to 
water at the temperature of our atmofphere, and refifts 
the adtion of acids as well as that of molt other folvents. 
As to the durability of thefe inflruments, few fubltanccs 
promif'e more than this, becaufe it may be foldered-afrelh 
in a damaged part. Any woven fubltance may be covered 
with it; it is only required that the .fubltance fliotil.d be of 
a nature not to be adted upon during the preparation, ci¬ 
ther by ether or by boiling water ; for thefe two agents are 
thofe which appear to me to merit the preference. Ar.tifls 
will frequently find an advantage in employing-ethefpias 
it requires lefs time ; fo that a perfon may make, in a (in¬ 
gle day, any tube he may have occalipn for. The expence 
of ether is very little, fince it is needful only to difpofe 
the caoutchouc to adhere ; and, being brought into that 
(late, the caoutchouc may be kept in a velfel perfectiy well 
clofed. It would aifo diminilh the expence of the ether, 
if, inflead of waffling it with a large quantity of water, 
there fhould be added to it only as much as it can take up.” 
A method of diffolving caoutchouc, without ether, for 
the purpofes of a varnifh, is as follows : Take.one pound 
of the fpirit qf turpentine, and a pound of the gum cut 
into very fmall pieces; pour the turpentine into a long¬ 
necked matrafs, which muff be placed in a land-bath ; 
throw in the gum, not all at once, but by little and little 
according as it is perceived to difl'olve : when it is entire¬ 
ly difTolved, pour into the matrafs a pint of nut or linfeed, 
oil, or oil of poppies, rendered deficcative in the tifual 
manner with litharge : then let the whole boil for a quar-, 
ter of an hour, and the preparation is finillied. This would 
make an excellent varnifh for air-balloons, were it not fo 
expenfive on account of the price of the gum. Another 
method, invented by Mr. Baldwin, is as follows : Take 
any quantity of the caoutchouc, as two ounces avoirdu¬ 
pois ; cut it into fmall bits with a pair of fciflars. Put a 
ftrongiron ladle (fitch as plumbers melt their lead in) over 
a common fire. The fire mult be gentle, glowing, and 
without fmoke. When the ladle is hot, much below a red 
heat, put a fingle bit into the. ladle. If black finoke if- 
lues, it will prefently flame and difappear, or it will, eva¬ 
porate without flame : the ladle is then too hot. When 
the ladle is lefs hot, put in a fecond bit, which will pro¬ 
duce a white fmoke. This white fmoke will continue du¬ 
ring the operation, and evaporate the caoutchouc: there¬ 
fore, no time is to be loft; but little bits are to be put in, 
a few at a time, till the whole are melted. It fhould be 
continually and gently ftirred with an iron or brafs fpoon. 
Two pounds, or one quart, of the belt drying oil (or of 
raw linfeed oil, which, together with a few drops of neat’s- 
foot oil, has ftood a month, or not fo long, on a lump of 
quick-lime, to make it more or lefs drying) is to be put 
into the melted caoutchouc, and ftirred till hot : and the 
whole poured into a glazed veftel, through a coarfe gauze, 
or fine fieve. When fettled and clear, which will be in a 
few minutes, it is fit for ufe, either hot or cold. 
Of the above gum, it is laid, the Chinefe make elafiic 
rings for lafcivious purpofes. Among us it is ufed by bur¬ 
geons, for injecting liquids, and by painters, limners, See. 
for rubbing out pencil lines or marks. For a botanical 
defeription of the tree which yields the caoutchouc, fee 
the article Iatropha. t 
CAP, f. [cap, Welffi; cceppe, Sax. cappe , Ger. cappe » 
Fr. cappa, Ital. capa, Spa. kappe, Dan. and Dutch; ca¬ 
put, a head, Lat.] The garment that covers the head ; 
Here is the cap your worfhip did befpeak.— 
•—Why, this w as moulded on a porringer, 
A velvet diffi. Shalefpeare. 
The enfign of the cardinalate : 
9 D 
Henry 
