M. Virey on the Discoloration of Coral Ornaments. 131 
10. On the application of Animal Empyreumatic Oil to the 
manufacture of Prussian Blue. — By M. Haenle. 
In attempting to render useful the empyreumatic oil produced 
in the manufacture of the muriate of ammonia, M. Haenle has 
obtained with this oil a lixivium for the preparation of Prus- 
sian blue, as rich in colouring matter as that made with horns 
or with blood. It produces a blue which is neither less beauti- 
ful nor less lively. For this purpose, M. Haenle reduces the 
animal oil into carbon, and reddens this carbon with an alkali. 
Jn this way, says he, chemists may, by means of the empyreu- 
matic animal oil, procure, in a short time, and without being in- 
commoded with the least smell, a prussiate of potash fit for a 
re-agent. To do this, a Hessian crucible, holding from 8 to 
lb oz. is filled half full with animal oil, and is placed among 
burning coals. As soon as the oil boils, it is set on fire, and the 
crucible is taken out of the furnace, and placed under the chim- 
ney. In proportion as the oil consumes, more is introduced in- 
to tne crucible ; and, after all is burnt, the tarry product is eal- 
, cined, till there rises from it a brown smoke, and till a part of it, 
put upon a cold body, hardens instantaneously, and presents the 
appearance of a porous and friable body without odour .-—An- 
nal. Gen. des Sciences Physiques. 
1 2 . On the Discoloration and Porosity of Coral Ornaments , and 
the method of Preventing it. — By J. J. Viiiey. 
It has been long known, that necklaces, bracelets, and ear-rings 
of coral, undergo, after being worn, a very remarkable change, 
and become extremely white and porous. Jewellers have no 
other remedy for this deterioration, than to remove the upper 
stratum of coral, till they come to a depth where no alteration 
had been produced. 
This change had been ascribed to the action of air and of 
light ; but this was found by experiment not to have been the 
case : and a discoloration never took place, unless when the co- 
ral had actually been worn as an ornament, in which case it ha& 
sometimes been completelv whitened, when used only two or 
three times upon the naked skin, and in heated apartments. 
M. Virey, therefore, very properly ascribes the discoloration and 
i 2 
