22 
POPULAR SClEi^OE l!5EWS. 
[February, 1890. 
[Original in Popular Science JVewi J 
ZINC. 
BY GEORGE L. BURDITT. 
Zinc, sometimes called spelter, is one of our most 
useful metals, and is widely distributed, although il 
never occurs alone. Sulphide of zinc and carbonate 
of zinc are its chief sources, and from these com- 
pounds it has to be distilled. The first step in the 
extraction of zinc is to reduce the ore to an oxide. 
Carbonate of zinc heated gives oxide of zinc and 
carbonic acid gas, (Zn C03 = Zn O + CO2.) Sul- 
phide of zinc roasted gives oxide of zinc and sulphur 
dioxide, (Zn S + 30=Zn O + SO2.) 
To get pure zinc from the oxide, the oxide is 
mixed with coal and heated in a retort. The zinc 
volatilizes, and comes out of the mouth of the retort 
as a vapor. Cadmium is always mixed with the 
zinc, and cadmium vapor comes out first. It is 
lighted, and burns with a brown flame. As soon as 
the zinc vapor begins to come off, the flame changes 
CO green. An iron cap is then placed over the 
mouth of the retort, through which the vapor 
passes, and is condensed into a fine dust. Gradu- 
ally the cap becomes hot and melts the dust into 
liquid zinc, which runs into moulds and is cast into 
blocks. 
The process described is called the Belgian pro- 
cess; there are two others, the Silesian and the 
English. The Silesian process differs only in the 
retort. The mixture of ore and coal is put in and 
heated, and the vapor passes out through a tube 
bent at right angles to the retort. The tube is kept 
cool, but not cool enough to condense the vapor 
into solid zinc. If this should happen, the pipe 
would become clogged and the retort would burst. 
In the English process, the retort consists of a 
tightly covered crucible, through the bottom of 
which passes a pipe. This pipe is stopped with a 
wooden plug, and the mixture of ore and coal is put 
into the crucible and heated. As the mixture grows 
hotter, the plug is converted into charcoal, allowing 
only the zinc vapor to pass through. The reaction 
which takes place in the furnace is, in all cases, 
2Zn + C=2Zn-|-C02. 
The pure zinc obtained by either of these pro- 
cesses is a bluish-white metal, having a metallic 
lustre and a crystalline fracture. It does not rust 
easily, and takes a good polish. Owing to this 
polisfi, it is used for making stage jewelry. Under 
the most favorable conditions, however, it rusts 
slightly, becoming carbonate of zinc. At ordinary 
temperatures it is brittle, and when heated to 100° — 
150° it becomes malleable, and is rolled into sheets. 
The specific gravity is 7.03, and the melting-point 
412°. It is quite volatile, burns with a green flame, 
and is one of the metals that expand on cooling. 
Next to iron, zinc is the cheapest of the useful 
metals, and, on account of this, has a number of 
uses. It is used in the galvanic battery. In this 
case, pure zinc would be very expensive to use, and 
it is not easily dissolved by acids. Impure amal- 
gamated zinc is cheaper, does just as well, and is 
readily dissolved in acids. Galvanized iron is iron 
coated with zinc to preserve the iron. If the zinc 
begins to rust, a galvanic couple is formed, the 
hydrogen collecting on the iron, thus preserving it. 
Zinc is alloyed with copper to form brass ; is used 
in making hydrogen, and is used in many places 
where iron and tin cannot be, on account of their 
rusting. Oxide of zinc, not being attacked by sul- 
phuretted hydrogen, is used in making white paint 
for laboratories. 
IN YE OLDEN TIME. 
When the "Best Friend," which was the first 
locomotive used in the South and the first built in 
this country, was put on the track of the South 
Carolina Railroad, its performances excited great 
curiosity. For a time its driver did quite a profita- 
ble business carrying the curious, in small parties, a 
few miles out on the line from Charleston and 
return, for a consideration. 
An old schedule and freight tarift" of the South 
Carolina road, now in the possession of an oflicer of 
that company, provided, among other things, that 
no dogs should be admitted to cars without the con- 
sent of the passengers; that conductors must require 
all guns or pistols in the possession of passengers to 
be discharged before the persons carrying them 
should enter the cars, and that no package should 
be entered on the conductor's freight list for less 
than 6\'i cents. 
After the explosion of the boiler of the "Best 
Friend," through the stupidity of its negro fireman, 
who held the safety-valve down a little too long, to 
avoid the annoyance of escaping steam, a special 
platform car was placed between the engine and the 
first car of the train, and loaded with bales of cotton 
as a means of protecting the passengers. 
In the early days of the South Carolina Railroad, 
before the telegraph came to be the handmaid of the 
railway, and when hours of delay in the arrival of 
trains were of less importance than are minutes 
now, the good people of Charleston were notified of 
the approach of a train by a flag displayed from the 
steeple of the railway station. It was the duty of 
an employe to keep a lookout from this steeple, and 
hoi.st the flag when he should catch the first glimpse 
of the smoke and steam of the locomotive. — Kailuay 
Ag.- ^^ 
INDUSTRIAL MEMORANDA. 
Hydrogen Occluded in Steel. — The theory of 
Dr. Mueller concerning the character of the gas 
occluded in steel, has been confirmed in a striking 
manner. The inventors of the famous Mannesmann 
method of making steel tubes, by rolling them 
eccentrically from a solid bar, sent to the Charlotten- 
burg laboratory two tubes closed at both ends, a 
partly finished product, therefore. The steel con- 
tained 0.46 carbon, 0.26 silicon, o.ojj phosphorus, 
o.oi sulphur, 0.23 manganese, and a trace of copper. 
The hollow cavity contained 911 c. cm. of gas at a 
pressure of 760 mm. Chemical analysis showed 
that this gas was composed of 99 per cent, of hydro- 
gen and only i per cent, of nitrogen, confirming 
Mueller's theory that the gas occluded in steel cast- 
ings is hydrogen. 
Co.MPRESSED Air AS Motive Power in France. — 
The use of compressed air as a motive power for tram- 
ways in France is extending. The system adopted 
is that invented 'oy M. Mekarski, director of the 
Nantes tramways, which have been open since 1879. 
Two years ago the system was successfully applied 
on the tramways at Nogent, in the neighborhood of 
Paris, and more recently on those of Berne and 
Limoges. This year it will be substituted for horse 
power on the tramways of Lyons. The inventor 
asserts that his system is far more economical than 
horse traction, — the cost of coal per day of a machine 
equal to 8 or 10 horse power being only $1.00, — much 
cheaper than electricity or steam power, and that 
machinery is simple and does not require a skilled 
mechanic to control it. The British consul at 
Nantes, in a recent report, states "that the tram- 
ways of that town, which are worked by the system 
ofM. Mekarski, alluded to above, continue to give 
satisfaction. The cars are comfortable and lun 
smoothly with little noise. They do not interfere 
with the general traffic in the streets, and their im- 
munity from accidents is remarkable. The average 
speed is about eiglit miles per hour; but it can be 
easily increased or moderated, and in case of need 
an almost instantaneous stoppage eflfected." 
Tlie Out-Door CLlorld. 
Edited by HARLAX H. BALLARD. 
President of the Agassiz Association. 
[P. O. Address, Pittsfield, Mass.] 
PROF. GUTTENBERG'S COURSE IN 
MINERALOGY. 
About a year ago, Professor Gustavo Gut- 
tenberg, then teaching in the Erie (Penn.) 
High School, undertook to give an Agassiz 
Association course of lessons in mineralogy. 
His plan is simple, and modeled somewhat 
after the excellent course previously conducted 
for us by Professor W. O. Crosby, of the 
Boston Society of Natural History. The 
course is conducted bv correspondence. 
Each pupil receives a set of minerals in a 
neat case, together with test-tubes, litmus 
paper, and streak-plate. Accompanying this 
case is the first lesson, in the form of a 
pamphlet, containing necessary definitions 
and concise instructions for a series of obser- 
vations on the first twenty-five specimens, 
which are numbered, but not labeled. There 
are blanks, on which the pupil records the 
results of his work. When the first blank is 
properly filled, it is returned to Professor 
Guttenberg, who corrects it, makes needful 
suggestions, and returns it, together with 
labels for the specimens alreadv examined. 
For all this work he makes no charge, and 
for the case of minerals and instrtunents, and 
the printed pamphlets, he makes only the 
nominal charge of one dollar. He divides 
the whole work into four grades, two of 
which were issued up to last August. Pro- 
fessor Guttenberg then received an appoint- 
ment as professor of biology of the Central 
High School of Pittsburgh, Pcnn., and his 
removal to his new post has caused a little 
delay in the issue of the third grade. This 
will soon be ready, however, and may be had 
upon application to him. All members of 
the A. A., and all subscribers to the Popular 
Science News, are cordially invited to take 
up this course of lessons. One who begins 
it in complete ignorance of mineralogy, will 
be surprised to find himself easilj' led along 
to a familiarity with all the more common 
forms of rock and mineral, and brought to 
a stage of progress whence advancement to 
higher work in determinative anahsis will be 
easy and rapid. 
^^►^ 
The organization of a Corresponding Geo- 
logical Chapter of the Agassiz Association — 
on a plan similar to the one so successfully 
carried out by the Gray Memorial Chapter — 
is now in progress. The undersigned organ- 
izing committee desires to brinjj this matter 
to the attention of every student and teacher 
of geology, mineralogy, and paleontology 
throughout the continent, whether a member 
of the A. A. or not. The object of the 
Chapter is to extend the knowledge of these 
