Acid wash

PROCEDURE
A clean and dry glass container (as specified in ASTM D 848) should be rinsed and then filled to the 7-ml mark with sulphuric acid of the strength specified in Table 1 for the type of sample to be tested. Thereafter the test sample material (e.g. wall wash sample) will be added to the container to bring the total volume to the 28 ml mark.
Stopper the container and WITH CAUTION, vigorously shake the mixture for about 40-50 seconds.
Allow the container to stand, protected from direct sunlight, for the period of time shown in the table below.
Without further delay compare the colour of the acid layer with the respective colour standards (as specified in ASTM D 848). For testing of chemicals in Group 1 in Table 1, the colour of the acid layer, as well as the colour of the oil layer, should be observed and recorded.

RESULTS
Group 1 samples pass the test only when the oil layer shows no change in colour and when the acid layer is not darker than the specified colour standard. Cloudiness or haze in the oil layer will not be interpreted as a change in colour. Group 2 and 3 samples will pass the test when the acid layer is not darker than the specified colour standard. The colour of the oil layer can be disregarded. Table: Acid Strengths and Standing Times