A n ether solution of purpurin is used to detect aluminum by means of a stabilizing effect of the dye lake on the foam produced by agitation of an ammonium hydroxide-ether mixture. The test is performed on the solution obtained by pouring 6 N NH4OH over the mixed hydroxides on the filter. 0.5 mg. of Al can be detected in the presence of 50 mg. of Cr, Fe, or other metals. In the presence of minute quantities of other elements, 0.001 mg. of Al can be detected without preliminary treatment.

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