166 
POPULAR SCIENCE NEWS. 
[November, 1890. 
the old chemists "vital air;" but its action upon 
the lungs is very violent if breathed undiluted for 
any considerable time. 
The distinguishing feature of oxygen is its great 
power of supporting combustion. When, by any 
rapid chemical action, light and heat are produced, 
combustion is said to have taken place. Heat is 
usually necessary to start the process, but afterward 
the heat given out during the process is more than 
enough to carry it on. In regard to combustion, all 
bodies may be included in one of three classes : 
1. Supporters of combustion; those whicfi, like 
oxygen, allow bodies to burn freely in them, but do 
not burn themselves. 
2. Combustibles; those substances which, like 
charcoal, actually burn in a gas of the first class, 
when raised to the proper temperature. 
3. Those bodies which, like sand, iron-rust, or 
earthy bodies in general, neither burn themselves 
nor support the combustion of other bodies ; they 
may be made red-hot, but they do not burn. 
The terms "combustible" and "supporter of 
combustion" are, however, merely relative; for, 
although hydrogen is ordinarily a combustible, and 
oxygen and chlorine supporters of combustion, yet 
these two last mentioned gases are quite capable 
of burning when surrounded by an atmosphere 
of hydrogen. All substances which burn in air 
burn in pure oxygen with greater brilliancy. If a 
glowing splinter is put into a jar of oxygen, it is 
lighted and burns with a very bright light. Sub- 
stances usually considered incombustible may burn 
violently in oxygen. For instance, take a steel 
watch-spring, coil it into a spiral, tip one end with 
sulphur and light it, and put the spring into a jar 
of oxygen. The spring burns with a dazzling light, 
and scintillates beautifully. The combination of 
oxygen with other elements is called oxidation, and 
the products are called oxides. Combustion is the 
combination of oxygen with another substance ; so 
that oxidation is really combustion, and vice versa. 
The cases considered above are cases of rapid 
combustion. At ordinary temperatures oxygen 
often enters into combination so slowly that the 
heat liberated is not perceptible (for oxidation 
always causes heat). This is the case when iron 
rusts in the air. This is called slow combustion; 
but this slow combustion is always accompanied by 
heat. A pound of iron will produce the same 
amount of heat, whether rusted in air or burnt in 
oxygen ; only in the first case it may take years to 
develop this amount of heat, and in the second only 
a few minutes. Under favorable circumstances oxi- 
dation may become so rapid as to raise the tempera- 
ture of a body to its ignition, when it bursts into 
flame, producing what is known as spontaneous 
combustion. This is especially the case in machine 
shops or factories, if piles of tow, used for wiping 
oil from machinery, or piles of oily iron-filings, are 
left lying about for any length of time. Although 
the combustible, or body which is burned, may 
undergo such a complete change of form as to dis- 
appear from sight, yet there is no destruction 
of matter or loss of weight during combustion. 
When a candle burns, it seems to be completely 
destroyed, leaving only traces of ash. However, it 
may be shown that there is no actual destruction 
of the candle's components, but that they have com- 
bined with a certain proportion of oxygen, forming 
carbonic anyhdride and aqueous vapor; and these, 
although invisible, really weigh more than the 
original candle, the gain in weight representing the 
amount of oxygen necessary to produce the change. 
Metals oxidize more rapidly in a moist than in a 
dry atmosphere. In the case of iron, the oxidation 
goes through the entire mass; but with other sub- 
stances, like lead and zinc, only a coating is formed 
on the surface, which protects the parts beneath 
from oxidation. 
Slow oxidation is constantly going on around us, 
although in such a quiet way as to be unnoticed in 
most cases. Oxygen, existing free in the atmos- 
phere, pervades everything, and shows an irresisti- 
ble desire to possess everything. The decay of ani- 
mal and vegetable matter is due to oxygen, which, 
by its combination with them, breaks them up into 
simpler substances. It is this slow oxidation which 
rids the earth, the air, and the sea of their impuri- 
ties — a sort of smouldering fire which consumes all 
waste matter. Its slight solubility in water enables 
it to remove impurities from below the surface 
of lakes, rivers, etc., thus keeping the water pure. 
The part played by oxygen in nature is of the 
greatest importance. It is a sort of keystone in the 
arch of chemical elements, holding them in their 
proper places by the vast number of combinations 
it makes with them. 
Of the pra<!tical consequences of Dr. Priestley's 
discovery, Prof. Liebig observes: "Since the dis- 
covery of oxygen, the civilized world has undergone 
a revolution in manners and customs. The know- 
ledge of the composition of the atmosphere, of the 
solid crust of the earth, of water, and of their influ- 
ence upon the life of plants and animals, was linked 
with that discovery. The successful pursuit of in- 
numerable trades and manufactures, the profitable 
separation of metals from their ores, also stand in 
the closest connection therewith. It may well be 
said that the material prosperity of empires has 
increased manifold since the time oxygen became 
known, and the fortune of every individual has 
been augmented in proportion." 
INDUSTRIAL MEMORANDA. 
Paper Pulleys. — According to Le Genie Civil, a 
French machine tool builder, M. Burot, of Angou- 
leme, is turning out paper pulleys for power trans- 
mission, based on the principle of the paper car- 
wheel. The pulleys have metal hubs and arms on 
which the soft paper mass is mounted and then 
compressed. After drying, the paper pulley is 
treated in a bath of linseed oil and resin to give it 
greater resistance against the influence of moisture. 
The pulleys are said to be very light and of low 
price, and to have given excellent results in practice. 
Tarred Pipes. — A simple and economical way 
of tarring sheet-iron pipes to keep them from rust- 
ing is as follows : The sections as made should be 
coated with coal tar and then filled with light wood 
shavings, and the latter set on fire. It is declared 
that the effect of this treatment will be to render the 
iron practically proof against rust for an indefinite 
period, rendering future painting unnecessary. It 
is important that the iron should not be made too 
hot, or kept hot for too long a time, lest the tar 
should be burned off. Hence the direction for the 
use of light shavings instead of any other means 
of heating. 
Brick Estimates. — Ordinary bricks are about 
eight inches in length, and, with the mortar joint, 
about half that in width, so that each brick on the 
flat will give a horizontal surface of about 32 square 
inches, or 41/2 bricks will cover a square foot. As 
ordinarily laid, there are nine courses to every 24 
inches, or 414 to the foot. Four and a half courses 
with 41/2 bricks to the course, will give 201/4 bricks to 
the cubic foot. Waste, cutting, and closer joints 
will easily require an allowance of 21 bricks per 
cubic foot, which will be found a very convenient 
figure for estimating the number of bricks required 
for a wall of given height and thickness, as it thus 
becomes unnecessary to find the cubic contents 
of the wall, but merely to multiply its face area, or 
the product of its length and height in feet, by 
seven-fourths of its thickness in inches, which, as 
the thickness is always some multiple of the four 
inches, is a very simple process. 
An Honest Gas Meter. — In view of the difficulty 
experienced by the general run of gas consumers in 
checking their gas bills against their meter register, 
an English inventor has devised a cash value indi- 
cator for gas meters. This consists of a dial placed 
on the front of the meter, and having around its 
edge figures, each representing 100 cubic feet of gas, 
from zero to 1,000. Under each of these figures is 
the cost of the amount" of gas represented by the 
figures at a stated price per i ,000 feet. The quantity 
consumed is indicated by a pointer, which is worked 
from the ordinary indicator of the meter, and after 
1,000 feet'of gas have been used this is indicated on 
another dial within the priced one ; the pointer then 
going on to indicate a second 1,000, and so on. The 
dial is made of cardboard, and should the price 
of gas vary, the dial will 'have to be removed and 
replaced by one showing the altered price. It is 
conceived that this arrangement will lead to the 
use of gas by many small consumers who distrust 
gas meters because they cannot understand them, 
and who doubt the correctness of gas bills because 
they cannot check them. 
White Lead by a Wet Process. — The older 
methods of producing white lead by the vinegar and 
fermentation process occupy a long period, and sev- 
eral methods have been in vogue to produce it in 
shorter periods. Recently Professor Maclvor has 
devised a method which has been developing gradu- 
ally into larger proportions, and proves a success, 
not only as to product, but also as to producing it 
as a commercial commodity, the cost of it being so 
reasonable as to permit it to come into active com- 
petition on price as well as quality. The process is 
as follows : Washed litharge is placed in a suitable 
tank, to which a solution of ammonium acetate is 
added, with constant stirring for six hours, and then 
allowed to settle ; after which the liquor is transferred 
to a second tank, where it is treated with carbonic 
acid gas. Tlfe pulp of lead carbonate has the mother 
liquor extracted, is then treated by washing until 
freed from all traces of ammonium acetate, when it 
is dried and ground. The product is said to be per- 
fectly white, a pure carbonate of fine texture, while 
economy of time is great, the entire pr»cess occupy- 
ing but a few hours. The ammonium acetate is 
recovered and is repeatedly used. 
PRACTICAL RECIPES. 
Stencil Ink. — Use shellac 2 oz., borax 2 oz., 
water 25 oz.,.gum arable 2 oz. Color with fine 
lamp-black, to desired consistency. You may use 
turpentine and lamp-black with a little linseed oil, 
or even glue and water with lamp-black. 
A Good Paint for shingle roofs, that can be 
be applied cold and^dries quickly, can be made as 
follows : One barrel of coal tar, ten pounds of as- 
phaltum, ten pounds of ground slate; mix by the 
aid of heat and add two gallons of dead oil. 
Photographic Films. — The composition of the 
films now so popularly used is said to be 9,000 grains 
of soluble cotton, 5,400 grains of camphor in 112 
ounces of methyl-alcohol, 2S ounces of fusil oil, and 7 
ounces of amyl-acetate. This solution is spread 
upon a " coated table" (a table which has had a 
solution of ozokerite in benzine poured over it and 
the latter evaporated) by means of a special sprink- 
ler; the film should not be over 3-1000 to 5-100O 
inch thick. After washing the film with a weak 
solution of sodium or potassium silicate it is dried 
and then coated with emulsion. 
