TUN 
T U It 
833 
T UN 
Wise than as having different velocities ; and 
us the small vibrations of the same chord are 
performed in equal times, and it is found 
true, in fact, that the sound of any body 
arising from any individual stroke, though ft 
grows gradually weaker, yet continues the 
same tone from tirst to last ; it follow's, 
that the tone is necessarily connected with a 
certain quantity of time, in making every 
single vibration; or that a certain number 
of vibrations, accomplished in a given time, 
constitutes a certain determinate tune ; for 
the more frequent those vibrations are, the 
■more acute the tone ; and, the slower and 
fewer they are, the more grave the sound, 
though performed in the same space of time ; 
so that any given note of a tune is made by 
one certain measure of velocity of vibrations, 
that is, such certain courses and recourses 
of a chord or string, in such a certain space 
of time, constitute a determinate tune. 
TUNGSTEN, a mineral found in Sweden, 
of an opaque white colour and great weight, 
xvhence its name tungsten, or ponderous stone. 
This ore was analysed by Scheele, who 
found that it was composed of lime and a 
peculiar earthy-like substance, which from 
its properties he called tungstic acid. The 
basis of the acid was found to contain a me- 
tal which was named tungsten, and which 
was obtained from the acid mixed with char- 
coal. 
Tungsten, called by some of the German 
chemists scheelium, is of a greyish- white co- 
lour, or rather like that of iron, and has a 
good deal of brilliancy. 
It is one of the hardest of the metals ; for 
Vauquelin and Iiecht could scarcely make 
any impression upon it with a tile. It seems 
also to be brittle. Its specific gravity is 17.6. 
It is therefore the heaviest of the metals after 
gold and platinum. 
It requires for fusion a temperature at least 
equal to 170° Wedgewood. It seems to have 
the property of crystallizing on cooling, like 
ell the other metals. 
It is not attracted by the magnet. 
When heated in an open vessel, it gradu- 
ally absorbs oxygen, and it is converted into 
an oxide. Tungsten seems capable of com- 
bining with two different proportions of oxy- 
gen, and of forming two different ox,ides ; the 
black and the yellow. 
The protoxide or black oxide may be ob- 
tained by heating the yellow oxide for some 
hours in a covered crucible. The peroxide 
or yellow oxide, known also by the name of 
tungstic acid, is found native in wolfram, 
and may be obtained from it by boiling three 
parts of muriatic acid on one o: wolfram. 
The acid is to be decanted off in about half 
an hour, and allowed to settle. A yellow 
powder gradually precipitates. This powder 
is to be dissolved in ammonia, the solution is 
to be evaporated to dryness, and the dry 
Inass kept for some time in a red heat. It is 
then yellow oxide in a state of purity. This 
oxide has no taste. It is insoluble in water, 
but remains long suspended in that liquid, 
forming a kind of yellow milk, which has no 
action on vegetable colours. When heated 
in a platinum spoon it becomes dark green ; 
but before the blowpipe on charcoal it ac- 
quires a black colour. It is composed of 80 
parts of tungsten and 20 of oxygen. Its spe- 
cific gravity is 6. 12. 
1. The sulphuret of tungsten is of a bluish 
Vol. II. 
| black colour, hard, and capable of crystal] iz- 
i ing. Phosphorus is capable of combining 
with tungsten ; but none of the properties of 
the phosphuret have been ascertained. 
The simple incombustibles do not seem 
capable of uniting with tungsten. 
The Elhuyarts alone attempted to combine 
tungsten with other metals. They mixed 
100 grains of the metals to be alloyed with 
50 grains of tiie yellow oxide of tungsten and 
a quantity of charcoal, and heated the mix- 
ture in a crucible. The result of their ex- 
periments is as follows : 
With gold and platinum the tungsten did 
not combine. With silver it formed a button 
of a whitish-brown colour, something spongy, 
which with a few strokes of a hammer ex- 
tended itself easily, but on continuing them 
it split in pieces. This button weighed 142 
grains. 
With copper it gave a button of a copper- 
ish red, which approached to a dark brown, 
was spongy, and pretty ductile, and weighed 
133 grains. With crude or cast iron, of a 
white quality, it gave a perfect button, the 
fracture of which was compact and of a whit- 
ish brown colour : it was hard, harsh, and 
weighed 137 grains ; and with lead it formed 
a button of a dull dark brown, with very little 
lustre, spongy, very ductile, and splitting 
into leaves when hammered: it weighed 127 
grains. 
The button formed with tin was of a lighter 
brown than the last, very spongy, somewhat 
ductile, and weighed 138 grains. 
That with antimony was of a dark-brown 
colour, shining, something spongy, harsh, 
and broke in pieces easily : it weighed 108 
grains. 
That of bismuth presented a fracture, 
which, when Seen in one light, was of a dark- 
brown colour, with the lustre of a metal, 
and in another appeared like earth, without 
any lustre ; but in both cases an infinity of 
little holes could be distinguisned over the 
whole mass. This button was pretty hard, 
harsh, and weighed 68 grains. 
With manganese it gave a button of a dark- 
bluish-brown colour and earthy aspect; and 
on examining the internal part of it with a 
lens, it resembled impure dross of iron ; it 
weighed 107 grain;. 
TUNGSTIC acid. The substance called 
tungstic acid by Scheele and Bergman was 
discovered by Scheele in 1781. This phi- 
losopher obtained it from the tungstat of 
lime, by treating it with nitric acid and am- 
monia alternately. The acid dissolves the 
lime, and the ammonia combines with the 
tungstic acid. The ammoniacal solution, 
when saturated with nitric or muriatic acid, 
deposits a white powder, which is the tungstic 
acid of Scheele. 
This powder has an acid taste, it reddens 
vegetable blues, and is soluble in 20 parts of 
boiling water. The De Luyarts have de- 
monstrated, that this pretended acid is a com- 
pound of yellow oxide of tungsten, the alkali 
employed to dissolve it, and the acid used 
to precipitate it. Thus, when prepared ac- 
cording to the above-described process, it 
is a compound of yellow oxide, ammonia, 
and nitric acid. Their conclusions have been 
more lately confirmed by the experiments of 
Vauquelin and Iiecht. This substance must 
therefore be erased from the class of acids, 
and placed among the salts. 
The real acid of tungsten is a yellow pow- 
der ; the method of procuring which, and its 
properties, Lave been already described under 
the denomination of yellow oxide of tung- 
sten. It ought rather, as Vauquelin and 
iiecht have properly remarked, to be classed 
among the oxides than the acids ; for it is in- 
soluble in water, tasteless, and has no effect 
on vegetable blues. It agrees with the acids 
indeed in the property of combining with 
alkalies and earths, and perhaps also with 
some metallic oxides, and forming with them 
salts which have been denominated tung- 
stats; but several other metallic oxides, those 
of lead, silver, and gold, for instance, possess 
the same property. These oxides, therefore, 
may be called acids with as much propriety 
as the yellow oxide of tungsten. 
I he affinities of this oxide, as far as they 
have been ascertained, are as follows: 
Lime; 
Barytes, 
Strontian, 
Magnesia, 
Potass, 
Soda, 
Ammonia, 
Glucina, 
Alumina, 
Zirconia. 
The manner in which it was produced is 
evident : tungstic acid is composed of oxy- 
gen and tungsten ; the oxygen combined 
with the carbon, and left the metal in a state 
of purity. 
1 UN 1C A, a kind of waistcoat or under* 
garment, in use amongst the Romans. They 
wore it within doors by itself, and abroad 
under the gown. The common people could 
not afford the toga, and so went in their 
tunics, whence Horace calls them populus 
tunicatus. The several sorts of the tunic 
were the palmata, the angustidavia, and the 
laticlavia. The first was worn by generals 
in a triumph, and perhaps always under the 
toga picta ; it had its name either from the 
great breadth of theclavi, or buttons, equal to 
the palm of the hand ; or else from the 
figures of palms embroidered on it. It was 
by these three different sorts of tunics, that 
the three different orders of the Roman 
people were distinguished in habit. 
TUNNAGE. See Tonnage. 
TUNNY. See Scomber. 
TURBITH, or Turreth-root. See 
Convolvulus. 
TURBO, the wreath, in zoology, a 
genus of insects belonging to the order of 
vermes testacea. The animal is of the snail 
kind ; the shell consists of one spiral solid 
valve, and the aperture is orbicular. There 
are 166 species ; of which the most remark- 
able are, 1. The littoreus, or periwinkle. 
This is abundant on most rocks far above 
low-water mark. The Swedish peasants be- 
lieve that when these shells creep high up the 
rocks, they indicate a storm from the south. 
They are eaten by the poor people in most 
parts of this kingdom. Young lobsters are 
said to take up their lodging in the empty 
shells of these animals, which has given oc- 
casion to a notion that periwinkles are 
changed into lobsters. But we apprehend 
the mistake to have originated from the cir- 
cumstance of the" cancer diogenes, or soldier- 
crab, which is a kind of small lobster or 
shrimp, naturally naked, which takes shelter 
in the cast shells of barbinated shell-fish. 2. 
Tire clathrus, or barbed wreath, has a taper 
shell of eight spires, distinguished by elevated 
