dryness. It is then dissolved in a
small quantity of alcohol and water, refiltered, and the filtrate
decomposed with ammonium carbonate. The original residue is treated with a
solution of ammonium carbonate, which dissolves arsenious acid and basic
zinc sulphate, filtered, and united with the first filtrate. When iron and
manganese are present, the filtrates are treated with bromine. The united
filtrates are boiled or examined volumetrically with sodium sulphide.

* * * * *

PETROLEUM AS FUEL IN LOCOMOTIVE ENGINES.[2]

[Footnote 2: Abstract of paper read before the Institution of Mechanical
Engineers.]

By Mr. THOMAS URQUHART.

Comparing naphtha refuse and anthracite, the former has a theoretical
evaporative power of 16.2 lb. of water per lb. of fuel, and the latter of
12.2 lb., at a pressure of 8 atm. or 120 lb. per square inch; hence
petroleum has, weight for weight, 33 per cent. higher evaporative value
than anthracite. Now in locomotive practice a mean evaporation of from 7
lb. to 71/2 lb. of water per lb. of anthracite is about what is generally
obtained, thus giving about 60 per cent. efficiency, while 40 per cent. of
the heating power is unavoidably lost. But with petroleum an evaporation
of 12.25 lb. is practically obtained, giving 12.25/16.2 = 75 per cent.
efficiency. Thus in the first place petroleum is theoretically 33 per
cent. superior to anthracite in evaporative power; and secondly, its
useful effect is 25 per cent. greater, being 75 percent. instead of 60
percent.; while, thirdly, weight for weight, the practical evaporative
value of petroleum must be reckoned as at least from (12.25 - 7.50)/7.50 =
63 per cent. to (12.25 - 7.00)/7.00 = 75 per cent. higher than that of
anthracite.

_Spray injector._--Steam not superheated, being the most convenient for
injecting the spray of liquid fuel into the furnace, it remains to be
proved how far superheated steam or compressed air is really superior to
ordinary saturated steam, taken from the highest point inside the boiler
by a special internal pipe. In using several systems of spray injectors
for locomotives, the author invariably noticed the impossibility of
preventing leakage of tubes, accumulation of soot, and inequality of
heating of the fire box. The work of a locomotive boiler is very different
from that of a marine or stationary boiler, owing to the frequent changes
of gradient on the line, and the frequent stop