US'EFtTL^PKOJEGTS. 



85§ 



ttai oils of lavender, and of turpen- 

 tine ; both of them speedily dilate 

 the caoutchouc, and are of no ^reat 

 price* The disagreeable smell of 

 the oil of turpentiije becomes pej;* 

 haps, in process of time, less dis- 

 agreeable than th?t of lavender. 

 This last is dearer, but the difier- 

 ence is not so great as it appears at 

 first, for we may make some advan- 

 tage of the oil of lavender that is 

 employed by the following opera- 

 tion ; upon plunging into alcohol 

 the elastic tube prepared with oil 

 of lavender, the alcohol charges 

 itself with the oil, and forms a very 

 good lavender-water J the same as 

 would be made by an immediate 

 mixture of oil of lavender with 

 spirit of wine. Immersion in this 

 liquor also serves to hasten the dry- 

 ing of the caoutchouc instruments, 

 thus made by means of essential 

 oils. I have made tubes with the 

 oils of turpentine and of lavender ; 

 both are much slower in evapora- 

 ting than ether. The oil of turpen- 

 tine particularly appeared to me 

 always to leave a kind of stickiness, 

 and I know not as yet, that we 

 have any means whereby to get 

 speedily rid of its smell. 



Nevertheless there is a solvent 

 which has not that inconvenience ; 

 it is cheaper, and may easily be 

 procured by every one ; this solvent 

 is water. I conceive it will appear 

 strange to mention water as a sol- 

 vent of elastic gum, that Hquid hav- 

 ing been always supposed to have 

 Vo action upon it. I myself re- 

 sisted the idea; but, reflecting that 

 ether by being saturated with water 

 is tlic better enabled to act on ca- 

 outchouc, and that this gum when 

 plunged ijito boiling water b^'comes 

 more transparent at the edges, I 

 presumed that this effect was not 



Vol. XXXVI. 



due sim.ply to the dilatation of hs 

 volume by the heat. I thought thatj 

 at that temperature, some action 

 might take place, and that a long 

 continued ebulhtion might produce 

 more' 'sensible effects. I was not 

 disappointed in my expectations, 

 and one of those tubes was pre- 

 pared without any other solventthan 

 water and heat. I proceeded in 

 the same manner as with ether; the 

 elastic gum dibtes but very little in 

 boihng water, it becomes whitish, 

 but recovers its colour again, by 

 drying it in the air and light. It is 

 sufiiciently prepared for use when it 

 has been a quarter of an hour in 

 boiling water ; by this time its edges 

 are somewhat transparent. It is to 

 be tur.icd spirally roiJnd the mould, 

 in the manner we described before, 

 and replunged frequently into the 

 boihng water, during the time that 

 is employed i.i forming the tube, to 

 the end tha": the edges may be dis- 

 posed to unite together. When the 

 whole is bound with packthread, it 

 is to be kept some hours in boiling 

 water, after which it is to be dried, 

 still keeping on the binding. 



If we wish to be more certaim 

 that the connection is perfect, the 

 spiral may be doubled; but we mHst 

 always avoid placing the exterior 

 surfaces of the slips one upon the 

 other, as those surfaces are the parts 

 which most resist the action of 

 solvents. This precaution is less 

 necessary when ether is employed, 

 on account of its great action upon 

 the caoutchouc. 



Itmip-ht be feared, that the action 

 of water on caoutchouc would de- 

 prive us of the advantages which 

 might otherwise be expected ; but 

 these fears will be removed if we 

 consider that the affinities differ ac- 

 cording to the temperatures ; that it 



A a IB 



