Part IV.] Puran Singh : Preparation of Tannin Extracts. 1 
which feeds the extraction vats. The general shape of this system of 
pans is similar to the Triple Effect System described in Plate II I, except 
that it has two pans instead of three. 
Triple Effect System. (See Plate III.)—This, consisting of three pans 
instead of two as in the Double effect system, is in general use in tanning 
factories. It ensures constant and economical working by its great 
evaporative capacity coupled with minimum consumption of steam. In 
the first pan the vacuum usually is 35-40 cm., in the second 50-56 cm., and 
in the third 60-69 cm., making the liquors boil at 84°C in the first, at 73°C 
in the second, at 54°C in the third. Thus 1 kilogramme of steam at 100°C 
entering pan No. 1 produces 1 kilogramme of water at 84°C and 1*015 
kilogrammes of steam from the tan liquors in No. 1, which in turn is con¬ 
verted into 1 kilogramme of condensed water at 73°C and 1*05 kilogrammes 
of steam from the tan liquors in No. 2, which in turn condenses into 1*05 
kilogramme of water at 54°C producing IT 25 kilogrammes of steam from 
tan liquors in No. 3. The steam from the tan liquors in No. 3 finally 
goes to the surface condensers for collection. Thus with 1 kilogramme 
of steam which in the Simple Effect System could only evaporate 1*015 
kilogrammes of water, a total of 3*19 kilogrammes of water has been 
evaporated in the Triple Effect System. 
Kestner’s Evaporator.—The improvements in tanning extraction 
machinery a re being effected very rapidly, and lately the Triple Effect 
System has been replaced by another still more efficient evaporator called 
KestnePs evaporator. This plant consists of a tubular bundle 7 metres in 
length and is constructed with simple, double, triple, and multiple effect 
to be heated either by the live steam from the boiler or escape steam from 
the engines. These evaporators occupy a very small space and are of 
simple construction, and having few joints they are unlikely to leak. 
They have another great advantage that they can be easily cleaned, allow¬ 
ing them to maintain their maximum capacity of output unimpaired. 
The liquor is equally distributed by a special arrangement through all the 
tubes of the bundle, which, it may be pointed out here, is a great advan¬ 
tage from the point of view of possible damage to products like tanning 
extracts owing to their being sensitive to heat. The difference is some^ 
what marked compared with other systems, thus for two sets of plants 
doing the same work, the ordinary quadruple effect would contain 15,000 
litres in concentration while Kestner's plant would have only 500. This 
difference indicates the application of a new principle in the construction 
224 
