Notes on the so-called " Black Lime " of China.
The following note on Black Lime, by Dr. A. P. Peak, Tientsin, appears in the Customs Medical Reports:—
This
substance is made by Dr. Williams to be " a kind of bitumen," and as it
has not been mentioned by any other writer with whose pages I am
familiar, possibly the correction of this mistake and the noting of two
uses to which it is put by the Chinese may prove of interest.
A
suspicion of its bituminous origin might arise from the facts that at
some plades there are found traces of petroleum in connexion with the
coal measures near which it is found, and that water in which it is
macerated sometimes shows an iridescent film upon its surface. The
substance in question is, however, amorphous graphite; and
although it is mined in localities near the coal beds, the Chinese
themselves insist that it has no connexion with them. The provinces of
Chihli and Shantung are mainly supplied from mines in the foot-hills of
the range bounding the great plain on the north-west, and much of this
material is shipped from Liu-li-ho, whence large quantities of lime and
coal are also forwarded, this city, situated at the head of one of the
affluents of the Peiho, being the distributing point for a large
mountain region. Near Liu-li-ho surface indications of petroleum seem
to abound.
One
of the uses before mentioned is its mixture with lime, to make a very
hard and durable plaster, used in situations that are exposed to the
weather. Because of this association, the Chinese call this "lime" like
the other, although, as they say, it has not the fiery principle of the
white lime.
A
peculiarity of this graphite is its avidity for water, not from
chemical affinity, as with lime, but from its great absorbent
qualities. The crude graphite, in lumps as it comes from the mines,
when exposed to contract with water, at once becomes permeated by it,
and falls into powder. In this state the particles slide upon each
other with the greatest ease, giving that lubricating quality which is
characteristic of graphite. When mixed with freshly slaked lime,
graphite in this state can be very thoroughly incorporated with it,
each one of the finely divided particles becoming imbedded in a matrix
of lime, and by laborious working and pressure, as the mortar sets the
mass can be so consolidated as to make, when hardened, one of the best
and finest grained mortars known, specimens of which can be seen in the
so-called " chunam " roofs.
The
superiority of this mortar is due solely to the physical character of
the little knife-edged, microscopic fragments of carbon; and yet,
strange to say, the use of silicious sand in mortar does not seem to
have commended itself to native builders.. I have never been able to
get one who was not familiar with foreign ways of building to
acknowledge its utility. True, it is somewhat difficult to obtain on
this great alluvial plain; still, where it can be had, so far as 1
know, loam is used in preference.
To
pass to the second economic use of graphite; this is the curious one of
dyeing cloth. The cotton garments universally worn by the middle
classes are coloured with the substance. The cloth is soaked in a hot,
aqueous mixture of graphite, in which there is a little glue; it is
then placed on a stone and mauled with wooden beaters; again immersed
and again beaten, the process being repeated many times witu each
piece, until the cloth assumes a deep and uniform tint attained by thus
mechanically forcing the fine particles of carbon more and more deeply
into the fibre of the cloth.
I
have rarely seen a more beautiful object than fibres scraped from the
cloth, loaded with brilliant, razor-like fragments of carbon, like
diamond dust, especially when viewed, in glycerine under a J immersion
lens. It is difficult to believe that such beautiful transparent
objects make up in mass the dull opaque plumbago.
This
process of dyeing, if we may call it so, I believe to be unique in the
art as practised at the present day. The colour is, of course,
indestructible by
