November 11,1871.] THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
385 
to have a quantity of distilled water near at hand, so 
that it can be at once added if, by the concentration 
of the acid, the action becomes at all violent. 
In driving off the excess of nitric acid, after the 
phosphorus has been dissolved, a considerable degree 
of heat will be required, and the greatest care should 
be taken that the acid has become quite cool before 
adding the water for dilution. If this is neglected, 
and the water is added to the hot acid, an explosion 
is inevitable, owing to the rapid change of the water 
into the gaseous form. Indeed, it would be much 
less dangerous to pour water into a ladleful of 
melted lead. 
For tliis, as well as all other operations in which 
solutions of acid or alkali are employed, the use of 
enamelled iron vessels must be avoided; nothing 
but porcelain, or at least Wedgwood, should be used. 
In this connection, the writer would protest against 
the use of enamelled vessels for any of the purposes 
of pharmacy in which an acid or alkali-proof mate- 
rial is required. He has never yet met with a vessel 
of this kind that was at all reliable, being either j 
of a material readily acted on, or pierced with minute j 
holes, exposing the underlying iron, and conse¬ 
quently contaminating everything with that metal. 
—Canadian Pharm. Jourii., August, 1871. 
THE PRINCIPLES OF GAS ILLUMINATION. 
[Continued from page 326.) 
The draught, or in-flow of air upon a flame of a given 
size depends greatly upon the velocity with ivhich the gas 
issues from the burner. With argands there is a special 
means of regulating the air-supply (viz. the chimney) ; 
but with all burners, whether argands or naked burners, 
the velocity with which the gas issues has an important 
influence upon the air-supply; and in the case of naked j 
burners (batwings and fishtails) this velocity of issue is, 
speaking roundly, the sole regulator of the air-supply. 
Every flame, by its heat, produces an upward current 
which draws in upon its sides the surrounding air; but 
(the heat of the flame remaining the same) the greater 
the ascending velocity of the gas the greater is the 
draught made by the flame, and the more air is drawn 
in upon it. A gas-flame rises into the air like a rapid 
stream entering or passing through a quiescent pool,— 
producing eddies, setting in motion and drawing in upon 
its side, in currents, the surrounding water. The more 
rapid the entering stream the greater the currents and 
eddies, the watery draughts, so to speak, which it makes 
in the pool; and these inflowing currents not only play 
upon the sides, but tend to mingle with the stream itself. 
Thus there are two constant and unavoidable causes of 
draught or air-supply to a gas-flame. Firstly, the as¬ 
cending power or velocity of issue which gas possesses, 
even when unignited, owing to its being lighter than 
the air; secondly, and chiefly, the fact that it is a flame, 
a source of heat, producing a partial vacuum which the 
surrounding air flows in to fill up. 
But with the gas-flame there is a special source • of 
disturbance, and that is the pressure under which it 
issues from the burner. The increased velocity thus 
given to the gas augments the draught upon the flame 
to an extent that is not counterbalanced by the quan¬ 
tity of gas consumed, the discharge of gas from the 
burner increasing only in the ratio of the square root of 
the pressure. In this way the gas-flame is brought into | 
contact with more air than it is able to bear without 
loss of illuminating power. Other points to be observed ! 
are that the supply of gas to all parts of the flame ; 
should be equal, and in an even and steady current, 
without any twist. 
The investigation as to the effect of the air-supply on 
the illuminating power yielded some interesting results. 
The size or height of gas-flames is notably diminished 
by increasing the draught or air supply. With an 
argand burner this draught can be regulated by means 
of the chimney, and the apertures at the bottom of the 
burner. Take Sugg’s London Argand No. 1, consum¬ 
ing five feet an hour of sixteen-candle gas. Without 
the chimney, we get a waving yellow flame about eight 
inches in height, and ocasionally smoking. The gas, in 
fact, extends itself upwards until, by the size of the 
flame, it comes in contact with the air to the requisite 
extent to produce entire, or almost entire, combustion. 
Put on a chimney, of the most suitable kind for this 
quantity and quality of gas, and the height of the flame 
is at once reduced by one-half \ nevertheless the illumi¬ 
nating power of the flame is increased by one-half l If, 
as is held by some, a slow rate of combustion were the 
best means of developing the illuminating power of gas, 
the tall flame which rises from an argand without the 
chimney ought to give the maximum of light. But the 
fact is otherwise ; for, when the chimney is placed on 
the burner, and the combustion of the gas proceeds 
much more rapidly than before, the illuminating power 
of the flame is largely increased. The explanation of 
this evidently is, that the brilliancy of the flame, owing 
to the intensity of the combustion, is so much increased 
as to far more than compensate the diminution in the 
size of the flame. Instead of a tall dull yellow flame about 
eight inches in height, we have a flame less than four 
inches high of brilliant white, which gives much more 
light. The cause of the shortening of the flame is the 
more rapid combustion of the gas, owing to the in¬ 
creased draught or air-supply produced by the use of 
the chimney. Hence it is manifest that rapidity of com¬ 
bustion, so far from occasioning a loss of light, may— 
and in this case does—greatly increase the illuminating 
power of burning gas. But if we still further increase 
the draught by using taller chimneys, we obtain oppo¬ 
site results ; a further diminution occurs in the size of 
the flame, which is not compensated by the increase of 
its brilliancy. The explanation of these opposite results 
throws an important light upon the real cause of the 
startling diversity of illuminating power obtained from 
gas when consumed in different burners and under dif¬ 
ferent conditions. 
As is well known, the Bunsen burner, in which air i3 
made to mingle with the gas before the point of ignition, 
gives a pale blue or violet flame which is almost light¬ 
less. But in proportion as the mingling of the air with 
the gas is diminished, by closing some of the holes in the 
stem of the burner, the flame becomes white and light¬ 
giving. A commingling of air with gas enormously 
diminishes, and may entirely destroy, the light-giving 
power of gas. But in what manner is this effect pro¬ 
duced ? 
First, take the case of a Bunsen burner. The air 
which mingles with the gas before the point of ignition, 
and which (so to speak j is burnt along with it, contains 
73 per cent, of nitrogen, which is a non-luminous, in¬ 
deed, incombustible body; and the result is, that the 
gas-flame being diluted with this incombustible body, 
cannot possibly attain the temperature which it would 
possess if burnt by itself,—part of the heat of the burn¬ 
ing gas being taken away in heating the intermingled 
nitrogen. But oxygen when in excess plays a similar 
part; for that portion of the oxygen of the air which is 
not needed to produce the combustion of the gas cannot 
burn, and simply dilutes the gas with a non-luminous 
body, which abstracts a portion of the heat generated by 
the burning gas. Hence, the flame of a Bunsen burner 
is, or may be, diluted by two non-luminous bodies— 
namely, by the whole of the nitrogen of the air admitted 
into the stem of the burner, and also by that portion of 
