34^ Separation ef Mucilage frtm Oils by Light. 



perty of gums,, or mucilage, to keep oil and water united in this ftate, I was induced to 

 fulpeft the prcfervation of mucilage in linfeed-oil. 



I had read in Doflie a method of preparing what he calls y<7* oil. It is effected by placing 

 linfeed-oil in a fhallow veffel expofed to the heat of the fun, and ftirring it frequently; in a 

 certain time it lofes its property of drying, thickens, and acquires a degree of tenacity that 

 makes it proper for a fize, or cement, for gilders, &c. A fimilar fubftance is alluded to by 

 Leonardo da Vinci. (Philof. Journal, IL 90.) " - 



Taking the exiftence of mucilage in this oil for granted, I conjectured that the alteration 

 produced in ks texture by Doflie's procefs, arofc from the evaporation of fome of its prin- 

 ciples, and the more intimate union of the reft, in confequence of that evaporation : to ve- 

 rify this conjedlure I tried the following experiment. I filled a half-pint phial full of lin- 

 feed-oil, corked and tied it fecurely over with a bladder. This I expofed to the heat of the 

 fun in fummer, during the whole day : after it had remained a few days in this Htuation, the 

 upper part of the phial was covered with drops, fimilar to thofe produced by holding a wet 

 bottle to dry before the fire. I then (hook it well, which made the contents look muddy, and 

 fet it to reft agwn- After a time it became clear, and a portion of tranfparcnt liquor, like 

 water, lay at the bottom. I then repeated the fliaking and fetting it to reft, till no ad- 

 ditional quantity of this fluid was feparatcd- 



By trying this experiment repeatedly upon oils procured from different places, I found 

 that fome oils afforded much more mucilage than others. From fome I feparated a third 

 part of mucilage ; from others a pint would not afford more than a table-fpoonful, and fome- 

 times lofs. Whether this difference in the rcfult was radically in the oils, or from a difference 

 in the proceflcs conduded by means fo variable as the^rieat of the fun, I am not able to 

 afccrtairu 



Upon trying the fame experiment with nut and poppy oil, I found the fame refult, but in 

 a different degree. The average quantity afforded by nut-oil was, I believe, not more than 

 a third part of the average of linfeed-oil, and the average of the poppy-oil was not fo much 

 as a fixth. In fome cafes, particularly of the poppy-oil, I did not obtain any. 



The colour of the oil always diiainifhed as the mucilage was abfliaCled ; but thp muci- 

 tilage was always as ccJourlefs as water. It is a queftion 1 will not pretend to decide, whe- 

 ther the colour of thefe oils depends upon the prefencc of the mucilage, or upon any other 

 principle which is deftroyed by the aflion of light. I have, in fome inftances, had the oil as 

 colourlefs as water. 



This decompofition of the oils, if it may be fo called, is curious, as proving the exiftence 

 of mucilage in them ; but as it is very troublefome, may it not be advifeable to prefer thofe 

 which have naturally the leaft mucilage in their compofition ? 



After p<Hiring the oils from the mucilage, I put feveral quantities of the latter together, and 

 found them mix without any difficulty. I mixed this mucilage with water, and found it 

 vnite with U in any proportion, without becoming turbid. I laid it upon plates of metal, 



expofing 



.%> 



