MISCELLANEOUS. 
COATING FOR GLASS RETORTS, &c, 
Profeffor Wurzer at Bonn, in a letter to Profeffor Gotling 
of Jena, fays: “It is not merely economy that makes us de- 
firous of obtaining good coating for glafs apparatus, but be- 
caufe the labour beftowed on many proceffes is often ren- 
dered entirely ufelefs by the veffel not being able to ftand the 
neceflary degree of heat. As circumftances during a certain 
time preveeed me from obtaining new glafs apparatus, I 
made various trials to fupply that deficiency, and found the 
following coating of the greateft fervice. I took fragments 
of porcelain coarfely pulverifed and well fifted, and as much 
pure clay, which I previoufly foftened with as much of a fa." 
turated folution of muriat of foda as was requifite to give the 
whole the proper confiftence, and then proceeded in the 
ufual manner. My glaffes,”” adds Profeflor Wurzer, which 
_ are coated with this fubftance, often ftand an incredible de- 
gree of heat wilhout breaking.” 
FREEZING OF MERCURY, 
The feyere cold which was experienced in London at 
Chriftmas afforded an opportunity to Mr. Pepys junior, 
and feveral ‘other able chemifts, to repeat the experiments 
of Mr. Lowitz, of Peterfburgh, on the production of eX. 
traordinary cold. ‘Ihe refult confirmed the truth of them. 
When the thermometer was at 17 of Fahr. a mixture of 
fnow and muriat of lime produced fuch a degree of cold as 
to freeze a quantity of mercury ina few minutes. It was 
then malleable, and, when broken, exhibited a fracture fimi- 
Jar to that of zink. : 
At the fame time the chemifts in Paris were occupied in 
repeating Lowitz’s experiments, C. Fourcroy and Vau- 
quelin by means of the fame mixture froze twenty pounds of 
mercury in a platina crucible in thirty feconds; mercury in 
OS | oe ou 3 a por- 
