National Republican., 1880-06-28
TESTING THE CITY GAS.
The Way 1t is Done by the Inspector
for the District.
Tho Use oftbe ePhoioinotor-How tho IliuIut
mating Power is Measured - Refined
Chemical Tests To Ascertain tho
Purity of the Product-rrovinG
metrcs--What Causes the
Pickering of the Gas.
what Can bo seon at Tho inspectors ofnce


a representative Of THE REPUBLICAN,
called short time ago at the office OF the
handsome and courteous United States gas
Inspector for the District of Columbia DR.
y. Calvert Ford, for the purpose of cnlight-
oning tho readers Of THE REPUBLICAN as to
tho modus opcrdnd Of testing the purity
ana Illuminating power Of the gas furnished
the people of Washington and GcoFgt town.
This work is one which requires tho ser
vices OF . skillful aud experienced chemist
in an unromitiinR attention 10 business.
Testing The Illuminating power Of the gas is
done by means of Bunseu's photomotcr, an
elaborate aud somewhat complex machine, tho
standard instrument for such purposes. The
idea Of Il photOmeter was first practically
realized by the celebrated Count Rumford in
application of tho w.l.known law of optics,
that the quantity of light thrown upon an
object by any luminous body is inversely as
| the square of the distance. RumfOrd adopted
the plan OF adjusting the lights at such
a distance from an upright rod that
tho shadow produced by each ON
n white screen should bo equal. lie
then measured the distances of the lights
from the rod, and the larger number of inches,
squared, divided by the smaller number,
squared, gave the Illuminating power of the
greater light in terms of the lesser. But this
method soon gave way 10 much more simple
aud accurate process devised by the famous
with meltod spermacoti it becomes translucent,
and ii spot DO left untouched in its centre
about the size of Il dime il is found that when
examined by reflected light (that is, light
from the same side AS the observer, the disc
will look white and the surrounding part
dark; but II the observer shifts his position to
the other side aud examines tho papcr by
transmitted light (lhat is, light from tie OPP
DUsite side OF the nsrument), the disc will
appear dark aud tho surrounding part light
and translucent Lastly, If two lights Of
equal intensity be placed one on each side of
the paper tho disc will disappear for then tho
light from ono side neutralzcs the other,
Snd there is no disposition 10 produce
either effect. This is the principle of BuHsens
photometer, which, us originally consl rucled
by Mr. King Of Liverpool, consisted OF u SIM
pie bar OF wood placed with its edge upper
| most, and FIRMLY supported at both ends. Tha
gas 10 be tested was burned at one end, and u
candle at the other, circular piece Of paper
being fitted 10 II socket, and made to slide
freely up aud down the bar, so tnat when
placed In such position that tho light from
| the gas was equal to the light from the cam
die, the value of the gas in terms of the can
die might be read of ON = scale attached
The instrument used at the gas inspectors
office in t,iis city, Is the abovo-described with
Gocdwin's improvement, which consists Of an
electromagnetic attachment and means Of
weighing the candle in siM. In addition TO
| this phOtomCtcr there is used as an auxiliary,
GOodwins improved loves Jet pinot ome er,
| instructed tO ascertain the candle power Of
coal by the height of flame while burning
through a circular orilce under varying pres
sure. To Iscnrtaiu tho purify OF the gas, it's
| freedom from phur aud ammonia within
the limits prescribed by the act OF congress of
June %, 1874, mot moro than twenty grains
| Of phur, and five grains of ammonia to each
100 feet OF gas, refined chemical tests are ap-
piled. which are absolutely accurate These
tests need not be otherwise described than by
saying that thoy arc those used by chemists
in their ordinary work, refined until perfect
minutoness Of accuracy, so to sp ak, are at
tanned. As II consequences, the gas furnished
by the Washington and Georgetown gas com.
pany Is remarkably free from impurities.
All defective metres in the city and All sus-
pcctcd Of defect are proved" by what is cal lod
the "prOvor," under the supervision of Mr..
Entwisle, a careful and skilihIl machmist.
All metres thus found at fault are handed
over TO the company, aud when found to 10
duly core ctod are sGmpei with the inspect
or's official stamp. The llckoring OF the gas.
which il so provoking an annoyance, osp ciilly
to newspaper men, is caused by the inoqu ,lity
OF pressure in the pipes, dependent on distance
from the gas works, aud is mol at all connected
with the metres.