GRIFFIN ON CHEMISTRY OF LI5IE SULPHITE FIBER. 285
built of iron or steel, and the lining of lead is attaclied in lunes by the
use of leaden headed bolts and clamps. This form of attachment has
caused more trouble than the others, as the bolts and clamps have
offered greater inducements for the liquor to penetrate to the shell, thus
requiring more time for repairs by their freriuency, and the extra
exposure of the shell to injury.
The remaining digester to be described is the Graham. It may be
built of any shape or size, stationary or rotary. The chief diflference
worthy of notice is in the attachment of the lining. In plain language,
the lead is soldered to the iron or steel sheets by the aid of chloride of
zinc. They are then rolled cold and assembled. The seams are polished
and filled in with lead by means of an autogenic apparatus.
The cellulose prepared by all the acid processes contains a consider-
able quantity of incrustating matter and lime salts, and hence is harsh and
brittle. "When a magne^ian base is used it is claimed that a softer fiber
is jjroduced; personally I cannot see much difi'erence. When the pulp
is first removed from the digesters it is beautifully transparent, owing
largely to the powerful bleaching effect of the sulphurous gas which acts
as a deoxidizing agent. Papers made for service for any length of
time should be reoxidized and bleached with hypochlorite of calcium.
If this is not done, the paper soon assumes a yellow color from exposure
to light and air.
The conclusions, therefore, which we draw are : That from a scien-
tific standpoint only two kinds of material are admissible for sulphite
digesters. Each must be supported by means of an iron shell. In the
one case the lead lining expands much more than its stronger companion,
is therefore subject to a great stress, which in time will produce fissures
and crystallization, and is permeable by the sulphurous gas, which has
a tendency in addition to produce hardness and brittleness. In the
other case the brick or tile lining expands much less than the iron shell,
and so this is liable also to crack if a temperature above 118 degrees C
A plant under either of these systems may be successful by good
management, neverth3less, without which no enterprise can succeed.
Sulphite fiber fills a much needed i3lace in the minufactare of paper
and is and will continue to be profitably made.
286 'DISCUSSION ON" LIME SULPHITE FIBER MANUFACTURE.
F. CoLLiNGwooD, M. Am. Soc. C. E. â€” The remarks of Major Mi-
chaelis about joining of metals recalls to my mind an experience at one
of the American Institute fairs. A substance called the "Cherry-heat
Welding Compound" was brought for examination before a committee
of which I was a member. It was claimed for it that it produced an
absolute Aveld of steel as strong as could be produced by the ordinary
methods, and at so low a temperature as to remove all danger of injury
to the steel. As it contained some metallic fragments and also a flux,
I asked what the fragments were, and was told they were iron.
To the question whether the introduction of iron between steel sur-
faces could possibly make a union equal to the steel ia strength, the
rei^ly was that it certainly did.
I then proposed a test. I was to obtain a weld of two pieces of
steel by the old method, and the inventor was to furnish one made by
his method from the same bar, this being a fine tool steel.
Each specimen was then turned down to proper size for test in a
Thurston's torsional machine, which was conveniently at hand.
The old style of weld broke at the full strengh of the steel directly
across the weld, through the solid bar; while that by the new process
separated along the welded surfaces, and at about the strength of fair
wrought-iron. The so-called weld was really a soldering with iron.
All the experience I have had with soldering bears out Major
Michaelis' statements; there is no mystery about it, no fusion or inter-
penetration of the parts joined. The solder is an alloy of some kind
which melts at a lower temperature than the metal soldered, and the
higher the temperature is, the more intimate the union, and the stronger
is the joint. When the parts joined are both heated to the melting point
of the solder, the latter flows, and not before.
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