Sartorius IB 31000 P Specifications download pdf (Page 26)

for half an h?ur at

100°C.

From now on the filter should only be touched carefully by a

smooth-tip forceps.

Ill. Remove filter from oven and place it in a desiccator for two hours in order to cool down

and

prevent the adsorption of water. Make sure that the silica gel in the desiccator is not

fully saturated with water.

the colour of the gel is pink, the gel is fully saturated and it

should be dehydrated first. The gel is blue in a dehydrated state.

IV. Take filter out of the Petri dish and weigh the filter as accurate as possible and record its

weight W

m•

V. PIace filter on the support plate of the filter funnel and replace the upper chamber. Clamp

the filter funnel together. Apply the vacuum very slowly to avoid tearing the filter. Pour

the weil-mixed sample with volume

into the upper chamber. Rinse several times with

distilled water to ensure that all the sediment is at the filter and no salt has remained in the

filter.

VI. Remove very carefully the filter from the support plate and put

in a Petri dish. Place the

Petri dish with filter in a oven for half an hour at

100°C.

VII. Remove filter from oven and place it in the desiccator for two hours.

VIII.

Weigh filter very carefully and record its weight W!d.'

IX. Calculate the concentration C:

(10.1.1)

The precision of this determination was determined with a suspension of China Clay. The dry China

Clay

was

suspended in distilled water, the concentration was 1

kg-m",

The volumes of the samples

were approximately

100

mI. The standard deviation found was 0.011

kg-m".

Defining the accuracy

as three times the standard deviation, the precision was about 0.03

kg-m".

10.2 Specificationsof filters and apparatus used

The filters used are membrane filters manufactured by Schleicher

Schuell (ME23), the pore size

is 0.15 p.m. The filter consists of a mixture of esters, nitrocellulose and cellulose acetate. This

composition gives the filter a great tensile strength. Furthermore it allows a relatively large flow rate

and the material will not stick to a Petri dish, for instance, after

has dried in an oven. For more

information about the filters the reader is referred to [19,20].

The filter funnel (Nalgene, Cat.No.315-0(47) is designed for filtration of liquids under full vacuum

using 47 or 50

membrane filters. An outline of the funnel is shown in figure

10.2.1.

The major

components are made of a special clear polysulfone, which has a chemical resistance to bases and

acids. For additional chemical resistance data see the instruction manual

[14].

In the

physico-chemical

laboratory three filter funnels are present and they are mounted on a Nalgene vacuum manifold

[16].

The desiccator is constructed of transparent acrylic to permit an undisturbed view of the contents. The

desiccator is manufactured by Nalgene and its dimensions

x W x D) are approximately 46 x 31

x 31

cm"

[15].

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Sartorius IB 31000 P Specifications Page 26

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