4.3.1 The apparatus should be set up under a fume hood to
remove toxic decomposition gases or in an open area where the fumes can be readily
dispersed. Although there is no explosion risk, when performing the test it is advisable
to have a protective shield, e.g. of suitable transparent plastics, between the observer
and the apparatus.
4.3.2 The trough is filled with the fertilizer
in the form to be offered for shipment and decomposition is initiated
at one end, either electrically or by means of gas burners as described
above. Heating should be continued until decomposition of the fertilizer
is well established and propagation of the front (over approximately
30 mm to 50 mm) has been observed. In the case of products with high
thermal stability, it may be necessary to continue heating for two
hours. If fertilizers show a tendency to melt, the heating should
be done with care, i.e. using a small flame.
4.3.3 About 20 min after the heating has been discontinued,
the position of the decomposition front is noted. The position of the reaction front can
be determined by difference in colour, e.g. brown (undecomposed fertilizer) to white
(decomposed fertilizer), or by the temperature indicated by adjacent pairs of
thermocouples which bracket the reaction front. The rate of propagation may be
determined by observation and timing or from thermocouple records. It should be noted
whether there is no propagation after heating is discontinued or whether propagation
occurs throughout the substance.