Pigments, Paint and Painting: A practical book for practical menTerry, George
Science
Pigments, Paint and Painting: A practical book for practical men
Terry, George
Paint; Painting, Industrial; Pigments
For the preparation of the raw mohr, for each charge of eighteen kegs
there are taken 80·64 kg. (117½ lb.) powdered and sifted sulphur, and
423·36 kg. (731½ lb.) of quicksilver.
The amalgamating kegs each contain 28 kg. (61½ lb.) of the charge, and
are given intermittent rotating motion by a rack and pinion driven by
a water-wheel. After an average of two and three-quarter hours, the
amalgamation is complete, and the raw mohr is taken from the casks.
For the sublimation, four furnaces are used, each with six pear-shaped
cast-iron retorts of considerable thickness. Each is charged with
58 kg. (127½ lb.) of mohr, the mouth covered with a loosely placed
sheet-iron helmet, the furnace being slowly fired; the combination
of the sulphur and the quicksilver then results in about fifteen
minutes, with a detonation. As soon as this operation (das Abdampfen)
is over, a clay helmet is placed over the retort, and the firing is
increased, so that after two hours and twenty minutes the excess
of sulphur evaporates from the tube. The condenser is now added
(Stückperiode--Cake-period) and luted, then the firing is still more
urged, whereupon the cinnabar volatilises and deposits itself upon the
glazed earthenware condensation apparatus (tube, helmet, &c.). After
four hours, the sublimation is complete, and there is furnished by
the helmet 69 per cent., by the tubes 26 per cent., by the condenser
(Vorlage) 2 per cent., cinnabar.
The grinding of the cake cinnabar takes place in four mills driven by
an undershot water-wheel. These mills have a fixed under and upper
movable stone, and the grinding is done with water. The vermilion which
leaves the spout and runs into glazed clay vessels has a temperature of
about 100° F., that of the air being 59° F. The millstones make forty
revolutions per minute, and after each passage of the charge are placed
nearer together.
(2) A German chemist named Fleck has discovered that when a warm
solution of hyposulphite of soda is added to a double salt of mercury,
such as chloride of mercury and sodium, the solution becomes acid,
and black sulphide of mercury is deposited. But if the hyposulphite
solution is added in excess, and the temperature is not allowed to
rise beyond 140° F., the solution remains neutral, and red sulphide of
mercury, or vermilion, is deposited. The least quantity of acid causes
the production of the black sulphide. The presence of a salt of zinc
facilitates the production of the vermilion. The best method is as
follows:--To four equivalents of hyposulphite of soda mixed with four
equivalents of sulphate of zinc in diluted solution, is added, drop by
drop, a solution containing one equivalent of corrosive sublimate. The
whole is gently heated for 60 hours, at a temperature of 112° to 130° F.
(3) The following account of vermilion manufacture in China appeared
over the initials T. I. B., in the _Chemical News_.
Public-domain text, read in full here on John Shaqi.
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