28
SECTION 2,
continued
2.6.4.3
Using an Ultrasonic Bath
An ultrasonic bath is effective in removing gas bubbles on most samples,
especially on viscous liquids (Cat. No. 24895-00 or equivalent). However, the
ultrasonic waves also may alter the characteristics of the turbidity-causing
particulates. Turbidity is dependent on the size, shape, composition, and refractive
index of the suspended particles. Excess application of ultrasound may alter
particle size and shape, and thus change the turbidity. In some instances, use of
ultrasound may compound the bubble removal task by fracturing gas bubbles, thus
making degassing more difficult. Use the following ultrasonic bath procedure.
1. Fill a clean sample cell with sample. Leave the cell uncapped.
2. Immerse the cell (
1
/
2
to
2
/
3
immersed) in an ultrasonic bath, and allow it to
stand until visible bubbles are expelled.
3. Remove the cell and install the cap. Thoroughly dry the cell, and apply a film
of silicone oil.
Bubble expulsion may take a few seconds to a minute or more. Follow this simple
procedure to avoid excessive application of ultrasound. First, apply ultrasound for
a short period of time, and again measure turbidity. Continue for several
repetitions, noting the treatment time and turbidity readings. If turbidity begins to
increase instead of decrease, the ultrasound waves probably have started to alter
the suspended particles. Note the treatment time before the turbidity increase, and
record it as the maximum time limit for ultrasonic treatment.
2.6.4.4
Application of Heat
DANGER
Make sure the cap on the cell is
loose. Heating a tightly-capped cell
may result in an explosion.
DANGER
Vérifier que le bouchon sur la cuvette est desserré. Le chauffage d’une cuvette bouchée
hermétiquement peut provoquer une explosion.
PELIGRO
Cerciórese de que la tapa de la célula esté suelta. Calentar una célula cerrada
ajustadamente puede originar una explosión.
GEFAHR
Der Verschluss muss lose auf der Küvette sitzten. Das Erhitzen einer fest verschlossenen
Küvette kann eine Explosion verursachen.
PERIGO
Tenha certeza de que a tampa na cela esteja solta. O aquecimento de uma cela tapada
apretada demais pode ocasionar uma explosão.
Avoid use of heat to accelerate degassing whenever possible. Heat may change the
characteristics of the suspended particles, and cause volatile components to come
out of solution. Gentle heating may be helpful in degassing very viscous samples
when combined with application of vacuum or ultrasound. If heating the sample is
necessary, do so only to the extent required to accomplish degassing. Cool the
sample to the original temperature before measurement.
Tài liệu sưu tầm của Trung Sơn - www.tschem.com.vn - 028.3811.9991 - [email protected]
Tài liệu sưu tầm của Trung Sơn - www.tschem.com.vn - 028.3811.9991 - [email protected]
