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REPORT OF THE CHEMIST. 39 
with brown coal, such a press can not be made tight, and after four 
or five may even refuse to close, except the surfaces be laboriously 
cleansed with iron scrapers. In chamber presses the peripheral joint 
is made between cake and cloth and not between cake and iron. 
From this fact alone it is far more perfect. Its form, however, if . 
roperly designed, is of yet greater importance and, presenting no 
onger necessarily a line of least resistance, reduces the chance of 
sludge, besides insuring, other things equal, a more uniform and 
complete displacement with reduced quantities of water by prevent- 
ing the formation of such water channels as those before described. 
If by any chance a small amount of semi-liquid material here runs 
in like manner, notwithstanding, this interferes in but half degree 
with a press joint now made between two thicknesses of the fabric 
instead of between iron and one such. Although in top and bottom 
fed chamber presses the liquor inter-ports of the individual chambers 
may be of greater diameter than those possible with frames, yet from 
liability to obstruction the center feed is to be preferred. 
Any filter press constructed for the use of brown coal or any of its 
congeners should be recessed for 1} instead of for 1-inch cakes. This 
statement will not remain true except that in all cases the wisdom of 
employing the matrix in excess is confirmed. A yet greater thick- 
ness in these might then perhaps prove still more advantageous were 
it not the limit at which, in such presses, the cloths have been made 
to stand. Without attempting an explanation of the fact, it remains 
that, with chambers of increased thickness, higher results per square 
foot of filtering area are attained, this dimension even doubled, curi- 
ously enough as it would seem, requiring but a very small fraction 
more of time for cake completion than before, so long as a slight ex- 
cess only of matrix is in each instance employed. This is best illus- 
trated in starch manufacture. Speed in filtration is, then, increased 
by this innovation, except for deficiency of matrix; arelative reduc- 
tion in the amount of sweet water to be dealt with is secured and 
proportionate time is saved in emptying. 
Since it consumes no more time to empty thirty chambers present- 
ing 400 square feet of filtering area than thirty aggregating fish 220, 
presses of the former size should alone be used for the purpose under 
consideration. Such are decidedly cheaper in first cost per square 
foot of filtering surface; are as readily handled and kept tight, and 
require, proportionately to the work done, fewer laborers. They 
occupy scarcely more space. 
The presses should be worked in batteries after the English plan, 
instead of by rotation; as practiced in Germany. This avoids a fall 
of pressure, with consequent loss of time and a cake ill suited to lixiv- 
iation in the other active presses, when one freshly prepared is set 
in operation. It also permits, which is of much consequence, low 
pressures at the start, which are gradually increased to high at the 
finish, a practice precluding all attempt at governing the pressure at 
the pump’s throttle by an attached pressure regulator. 
A precipitate invariably following evaporation, by whatever means 
accomplished, of juice filtered through brown coal, the filtration of 
sirup was accorded some study. For this purpose from 12 to 15 per 
cent. of lignite on the weight of sugar operated upon was found 
necessary to satisfactorily rapid work, previous treatment notwith- 
standing. Again the improvement in purity was not marked, aver- 
aging 0.82; that in color being the more conspicuous result, at about 
40 per cent. of this removed. 
