Technical Chemistry. 265 
distinctness through red, orange, yellow, green, nor even purple media; 
they are on the other hand well shown by a certain thickness of a solu- 
Yellow solutions when com- 
ith the blue glass or blue solutions render the circulation invisible, 
and it does not reappear till the yellow solution has been made so dilute 
a he ade 
great extent transparent, to all their rays and therefore fail to cast shad- 
esl if new ma ga- 
ged in the study of the physiology of the eye. 
y, May 14th, 1860, 
Tzouyrcar, Cuemistry, 
1. Care of Platinum Crucibles—In connection with some sensible re- 
marks Upon the use of sand in cleaning platinum erucibles,—a_ practice 
hich, with Berzelius, (Lehrbuch der Chemie, 1841, 4th Aufl. p. 516,) 
0 n 
that 4 crucible is used, Erpmann explains the cause of the gtay coating 
at forms upon platinum crucibles whenever they are ignited in the 
m.oF Bunsen’s gas-burner. Keitud 
| This Coating has given rise to much annoyance and solicitude among 
chemists, Indeed it has often been asserted, that the use of Bunsen’s 
* Mr Wm. B . f these facts were commu- 
icated 1. 2 B. Taylor of Washington to whom some ©: ge amram 
ned by Prof. J. pas was able = trace this appearance, though with diminish- 
"0 distinctness, through’plates of bluish-green and yellow glass. 
AW. JOUR. SCL-SECOND SERIBS, Vou. XXX, No. 6.—SEPT., 1860. 
oH 
