Building Materials, Third Edition

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™ IPI

The average moisture content of each sample is calculated as:

M =

1

n

m

P

× 100

where M = average moisture content of sample (per cent)
m = corrected moisture meter reading in any sector of sample (per cent)
P = number of sectors measure

The average of moisture content of all samples tested from a lot is calculated by the formula for
checking conformity of a lot to the requirements of the relevant specification:

M =

(^1100)
P
m
n



where M = average moisture content (per cent)
m = moisture contents of individual samples (per cent)
n = number of samples selected from the lot
h— wX This method is used for species like
deodar containing volatile oil or extractives. It is also used
for timber impregnated with volatile or non-volatile
chemicals that are likely to interfere with the correct
determination of moisture content by oven-drying or
electrical moisture meter methods.
The apparatus for the test consists of distillation flask
with indirect heating arrangement, cold water-cooled
condenser of the cold finger type (Fig. 4.20), water trap,
scales of accuracy 10 mg, and scalable weighing bottles.
About 50 g of each test sample is distilled till no more
water collects in the water trap. Any water condensed
elsewhere in the trap is washed down into the trap with the
help of a solvent spray. Sufficient time is allowed for a clear
separation of water and solvent (xylene or toluene) in the
trap. Any bubbles inside the water collected in the trap are
removed by tapping it. The moisture content of each sample
is calculated by the following formula:
M =
1
W 100
W
M
MM



where M = moisture content
M 1 = mass of test specimen before distillation
MW = mass of water

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The characteristics and suitability of timbers are given in Table 4.2.

p



2R

PH h



—

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