while making Amber Varnish.' 279 



iJiiring the operation, and until the heated substance had ac- 

 quired the proper degree of fluidity, a great deal of succinic 

 acid was disengaged. 



Every artist has had an opportunity of making the same 

 remark ; but whether they mistook, the real nature of this 

 salt and its properties, or considered it only as essentially in- 

 herent in the quality of the varnish, no one has hitherto at- 

 tempted, as far as t know, to derive any advantage from it. 

 Those, however, would be in an error who should infer from 

 what ha:> been said, that good varnish ought to be free from 

 succinic acid ; on the contrary, it is very probable, that on 

 the addition of drying oil and essence, which ought to in- 

 crease the fluidity of the amber, this matter can still furnish 

 some of it, and even in abundance. 



1 should deviate from the real object I have proposed in 

 this notice, were I to relate the diiferent processes employed 

 in the preparation of this vaniish : I shall only observe, that 

 as this operation is performed for the most part with the con- 

 tact of the air, and over an open fire, and in varnished 

 earthen vessels, the aperture of which is from four to five 

 inches in diameter, — when the matter is sufliciently pene-- 

 trated bv caloric, a part of the succinic acid, become free, is 

 exhaled as mere loss into the atmosphere, while a very large 

 quantity is fixed to the sides of the matrass, under the form 

 of very fine delicate needles, sufliciently white to have no 

 need of purification*. Each matrass, containing twenty- 

 tour ounces of amber, (a common dose,) can furnish from 

 eighty to ninety grains of acid, without in any manner les- 

 sening the quality of the varnish f- It is proper to observe 

 also, that one ought to seize the moment when the succinic 

 acid is disengaged, to separate it ; and this disengagement 

 takes place a little time before tlie addition of the oxyge- 

 nated or drying oil. If the operation be deferred, the greater 

 part of the product will be lost. The motion indeed neces- 

 sary to be given to the spatula, to effect the mixture of the 

 oil with the amber, detaches a great deal of volatile salt. 

 All hope, therefore, of collecting it must be lost when es- 

 sence of turpentine is added j as this oil, vaporized by the 



• The acid obtained by the first operation is indeed very pure w! en the 

 vessel is nt-.v, but in the bubsciiueut openitions it becomes n)ore coloured. 

 Ri-cmrsc mav be had to tl;e processes of p irific;itiun indicated by Port. 

 iV'tists will Knd it of advantage to enipiov 'iiatrrisses of copper: as these 

 v:isels are easily cleaned, thev will always funiish the same product. 



■f- I ascertained this fact by several experimen's. pi rfbrmed both in iny 

 <Hvn laboratory and in that of iVI. ToDntlicr, coach-paiiiicr, who is cx- 

 ccediogly v.tli vervctl ia tl»is branch ni the arts. 



S 4 heat 



