178 Estimation of Nickel in Pyrrhotites and Mattes. 
vanometer needles, and for delicate torsion apparatus, can be 
expeditiously formed in this way, and by the use of very thin 
adherence, are serious disadvantages. These are entirely 
avoided by the use of an unalterable metal like platinum; and. 
though for instruments of the largest size the process here 
' described may be found impracticable, for those of more mod- 
erate dimensions there is every reason for believing it may be 
employed with complete success. The labor and time required 
for its application are indeed drawbacks; but there is compen- 
sation for this in the important cireumstance that the mirror 
comes out of the receiver with a surface of inimitable perfec- 
tion, which would in fact only be injured by any of the ordin- 
ary methods of polishing. 
Yale College, August 8, 1877. 
Art. XXIIL—A new and ready method for the Estimation of 
Nickel in Pyrrhotites and Mattes; by MARGARET S. CHENEY, 
and ELLEN Swa.iow RicHarps. 
WE had occasion several months since, to make a number of 
determinations of nickel in mattes where, for commercial rea- 
separation of iron as a basie acetate. (Fre s, page 36e. ) 
This method requires considerable analytical skill and practice 
in its use. The large dilution and subsequent evaporation nec- 
essary render the operation a tedious one, even without the re- 
_ peated re-precipitations which are indispensable to a complete 
separation. : 
The method based upon the behavior of neutralized solutions 
at the boiling point (Fresenius, page 362), which we personally 
prefer to use, is open to the same objections. The process of 
