f. Bunsen on the Washing of Precipitates. 333 
of “seg greater pressure, more easily overcome in the new 
minutes and 1050 cub. centims. of water to effect a washing to 
ssda5 part; the new, on the contrary, only 12 to 14 min- 
utes, and not more than 39 to 41 cub. centims. of wash-water. 
x 
taining 02436 erm. Cr20? in a water-bath at 100° C. requires 
at least five hours ; and, moreover, bringing the dried precipi- 
tate into the crucible, burning the filter, and gradually igni- 
ting the mass is in the highest degree tedious and troublesome. 
All this expenditure of time and labor may be saved by em- 
Ploying the new method. By its means a precipitate is as 
completely dried upon the filter in from 1 to 5 minutes as if 
ithad been exposed from 5 to 8 hours ina drying-chamber ; and 
it can immediately, filter and all, be thrown into a platinum or 
Porcelain crucible and ignited without the slightest fear of its 
urting. By operating in the following manner the filter 
burns quietly without flame or smoke ; this phenomenon, al- 
though remarkable, easily admits of an explanation. The 
Portion of filter-paper free from precipitate is tightly wrapped 
‘ound the remainder of the filter in such a manner that the 
Pycbitate is enveloped in from four to six folds of clean paper. 
the whole is then dropped into the platinum or porcelain cru- 
cible lying obliquely upon a triangle over the lamp, and pushed 
down against its sides with the finger. The cover is then sup- 
ported against the mouth of the crucible in the ordinary way, 
and the ignition commenced by heating the portion of the 
_ ucible in contact with the cover. When the flame has the 
__ Proper size and position, the filter carbonizes quietly without 
3 e ca 
Moved a little toward the bottom of the Bee -" ies some 
_ ‘me the precipitate appears to be surrounded only by an ex- 
mely thin envelop of carbon, possessing exactly the form 
