1094 GEOLOGY OF OHIO. 
plate glass, a short cylinder of glass, having both edges ground, was 
placed, and above this a second plate of glass, having a hole bored 
in it near the edge. Into this hole, lined with a collar of rubber, a 
funnel holding the crucible was placed, and inside the cylinder, below, 
was placed the beaker to catch the filtrate. Into the side of the cylin- 
der a hole was bored, into which a rubber cork and glass tube were 
fitted, and to which the Bunsen suction pump was attached. A three- 
way stop-cock in this tube turned on suction or admitted air so as to 
avoid the running back of water from the pump when suddenly stopped. 
The apparatus can be easily constructed; the cylinder was made by cutting 
off the top and bottom of an acid bottle, and the plate of glass and 
cylinder were bored by a piece of brass tube and emery powder. The 
great advantage was in having the top plate movable as to position, so 
that the stem of the funnel could be~placed against the side of the 
beaker and the beaker and filtrate removed; in fact, the apparatus is as 
convenient as an ordinary filter stand in respect to handling funnel 
and filtrate. 
In some limestones, water was determined directly by heating in a 
glass tube and catching the vapor in a calcic chloride tube. 
In the course of analysis, when an unusual amount of ammoniac 
chloride had been formed (as in the case where lime had been redis- 
solved) the filtrate from the magnesia was evaporated nearly to dryness, 
and the ammonia salts decomposed by heating with nitric acid as de- 
scribed by Dr. J. Lawrence Smith, and the so purified liquid diluted 
and reprecipitated with ammonia, thus yielding, in some cases, a further 
trifling precipitate of magnesia (which seems to be “kept cs > by a 
large excess of the salammoniac). 
Furnace slags were analyzed by the same general methods as iron 
ores. 
Pia-IRons. 
The number of pig-iron analyses made was small ; hence, but a short 
statement of the methods used will be given. | 
The carbon was determined by dissolving the iron in double 
chloride of copper and ammonia, filtering out the residues on to asbes- 
tos, then converting the carbon to carbon dioxide by Ullgren’s chromic 
acid method and absorbing in potash bulbs. The potash bulbs were 
protected by a small chloride of calcium tube placed both before and 
after them; this was found necessary to insure complete freedom from 
