154 
POPULAE SCIENCE NEWS. 
[October, 1S90. 
of minute particles of the metal from the 
rock in which it occurs. 
Pure gold is so soft that it would soon be 
worn awaj' by use, and it is always alloyed 
with a varying proportion of copper or silver, 
usually about one-tenth. Pure gold is said to 
be 34 carats. Thus, i8-carat gold contains 
18 parts of the pure metal in 24, or, is three- 
quarters pure. Many cheap alloys of base 
metals can be made which very strongly 
resemble gold in color and lustre ; but, in the 
absence of a complete chemical test, the high 
specific gravity of gold (19.3) is the best test 
of its purity, though this has been ingeniously 
imitated by covering the heavy but cheaper 
metal, platinum, with a layer of gold. 
Iron pyrites and other yellowish minerals 
are constantly being mistaken for gold, by 
inexperienced persons, much to their disap- 
pointment, but a very simple test will show 
whether a doubtful specimen is really the true 
metal. Gold is very scctile, that is, it can 
be cut and shaved with » knife, like a piece 
of wood or horn ; while pyrites and other 
worthless minerals will crumble under the 
knife-blade like a lump of sugar. If any 
reader of this article ever finds a yellowish 
mineral which can be cut without crumbling, 
it is worth a more thorough test ; otherwise 
he may as well save himself unneccessary 
trouble and disappointment. 
Very few chemicals have any effect on 
gold. Selenic acid will dissolve it, but few 
chemists have ever seen this very rare sub- 
stance. A mixture of nitric and hydrochloric 
acids (aqua rcgia) will also dissolve it, 
forming a chloride of gold ; and so will a 
solution of chlorine gas in water. In both 
of these liquids a peculiarly active form 
of chlorine, known as nascent chlorine, is 
present, which probably unites directly with 
the metal. 
Gold, like all the noble metals, is unchanged 
by heating in the air. Its oxides can be ob- 
tained by chemical reactions, but they are 
very unstable, and easily reduced back to the 
metal. The chloride above referred to is the 
only salt of any practical importance, and is 
used to produce the beautiful Purple of Cas- 
sius, a compound of tin and gold of uncertain 
composition, but yielding a magnificent ruby 
color when melted into glass. A hundreth 
of a grain of gold will deeply color a cubic 
inch of glass. The most extensive use of the 
chloride is, however, in photography, where it 
is used to "tone" or color prints on silvered 
paper. This darkening of the prints is due 
to the decomposition of the salt and the depo- 
sition in the picture of finely-divided metallic 
gold, which not only gives it the desired color 
but renders the image very permanent. 
By beating out between pieces of membrane, 
gold may be formed into leaves of such thin- 
ness that 282,000 of them will only make a 
pile one inch in height. A single ounce 
of gold may thus be spread over one himdred 
square feet. In the manufacture of gold 
thread for embroidery, a cylinder of silver is 
covered with gold and afterwards drawn out 
into wire. In this way six ounces of gold 
have been made to yield over two hundred 
miles of gilt wire. Even at this extreme 
tenuity the coating is perfect, and does not 
rust or tarnish. 
The thin leaves of gold mentioned above 
have the familiar yellow color by reflected 
light, but are partially transparent, and by 
transmitted light show a green or blue tint. 
If gold leaf adhering to glass is heated to the 
boiling-point of oil for some time, it will 
become quite transparent and invisible by 
transmitted light, though still showing the 
usual golden color by reflection. When gold 
is deposited on glass by an electric spark, the 
finely divided metal transmits rub}', violet, 
or green light, according to the thickness 
of the deposit, though reflecting the usual 
yellow metallic luster. 
Bromide of gold has lately been used to 
some extent in medicines, but it probably has 
no particular advantage of the other salts 
of bromine, while the high cost would always 
form an objection to its general use. A quack 
remedy said to contain gold has been adver- 
tised as a cure for drunkenness, but an analy- 
sis has failed to detect the precious metal, 
which, even if it were present, would have no 
such effect as is claimed for it. Taken in 
considerable quantity, the salts of gold are 
said to be distinctly poisonous. 
From the time of the alchemists the arti- 
ficial production of gold by transmutation 
from other elements has been a favorite pur- 
suit of mankind, and even at the present day 
there are probably a few unbalanced persons 
engaged in the quest of the "philosopher's 
stone." It must be admitted that the tendency 
of modern chemical thought is towards re- 
garding the different elements as either com- 
poimd bodies, or diflerent forms of one 
primitive material substance ; but whatever 
may have occurred in the early ages of the 
universe, or whatever may be the true con- 
dition of matter at the present day, not a 
single fact has ever been observed which 
would indicate the possibility of changing 
one so-called element into another. And 
while we cannot say with absolute certainty 
that lead, for instance, can never be changed 
into gold, the improbability of such a trans- 
formation is so great, that we may place it 
beyond serious consideration ; and until further 
investigations open up avenues of research 
at present unknown to us, we must be con- 
tent to laboriously dig out of the ground the 
stores of the precious metal that nature has 
supplied to us ready made, and shall search 
unsuccessfully to repeat transformations of 
matter, which, if they ever took place, occurred 
at so early a period in the history of our uni- 
verse that the human mind is unable to com- 
prehend the number of years which would 
indicate its remoteness ift time. 
[Specially Reported for PopuUir Science News. I 
INDIANA'S WELCOME TO THE AMERICAN 
ASSOCIATION. 
When Indianapolis was chosen for this year's 
meeting of the American Association for the Ad- 
vancement of Science, there was a feeling — pjfl-ticu- 
larly in the Eastern States — that the attendance 
would be but small, and limited to working 
scientists. "Those who go to Indianapolis," it 
was said, "will go there for science alone; what is 
there in Indiana to compensate a holiday-maker for 
the expense and fatigue of getting there?" The 
facts were overlooked that Indiana is distinguished 
for the number and efficiency of its scientific socie- 
ties, and that it contains the almost unique feature 
of a supply of natural gas over a large district of its 
territory. Indianapolis — and Indiana, too — intended 
that this meeting should be a great success, and no 
trouble or expense was spared to secure that end. 
Successful it truly was in every way, and especially 
in the very direction in which failure seemed to 
threaten. Stynuch was this the case that, although 
the work of the sections was of the average value, 
— in one or two instances even rising higher, — and 
the addresses of the president and vice presidents 
were of unusual interest, this Indianapolis meeting 
will be chiefly remembered for the excursions and 
other accessories in connection with it. 
The trip through the Indiana gas region, given to 
the members of the Association by the local com- 
mittee, commanded universal admiration for the 
completeness of the arrangements, whereby the 
special train of eight cars was passed from one line 
of railroad to another, and nearly four hundred 
people were enabled to enjoy with ease and comfort 
sixteen hours of novel experiences. Leaving In- 
dianapolis at 7 A. Nf., the train ran first to Nobles- 
ville, from which place Indianapolis largely draws 
its natural gas. Here a well was opened and the 
gas lighted. Burning with a large flame, the full 
pressure of 300 pounds to the inch was turned on. 
when the gas roared out as it used to roar from the 
great Pennsylvania "blowers," throwing up the 
flame to a height of seventy-five or eighty feet. 
Before the day was over the excursionists became 
almost bewildered with the repetition of this exhibi- 
tion, as on the approach of the train every well 
within sight, large or small, roared and sent up a 
sheet of flame. While the visitors enjoyed this 
sight, — to many of them a novel one, — there were 
some among the scientists who deplored the waste 
involved, and lost no opportunity of suggesting 
that, though apparently unlimited, the supply of 
this precious fuel is, in reality, a fixed and definite 
quantity, which, when once exhausted, cannot be 
renewed. 
From Noblesville the train ran to Kokomo, the 
pioneer natural gas city of Indiana, which, from 
being an ordinary county seat town of 4,000 inhab- 
itants in 1SS6, when the drill first set free the 
screaming flames, has now become a manufacturing 
center of 12,000 people, with thirty-one industries, 
all dependent on the natural gas. Of these, because 
newest in this country, the most interesting to the 
members of the Association was the plate glass 
factory. Here they were permitted to witness the 
process of making the pots in which the materials 
for the glass are melted. They then stood by while 
one of these pots, fresh from tlie furnace, was lifted 
and overturned over an iron table, its contents 
pouring out in a glowing, golden stream, soon to 
be rendered even and oblong by the passage over it 
