Subject heptane-modified

The following TLC procedure is useful for separating sulfamethoxazole from sulfanilic acid and sulfanilamide (16). Using silica gel G plates and a solvent made from a mixture of alcohol, n-heptane, chloroform, and glacial acetic acid (25 25 25 7), spot 0.1 mg of sulfamethoxazole dissolved in ammoniacol methanol and subject to ascending chromatography. After development of at least 12 cm, the plate is air dried and sprayed with Modified Ehrlich s Reagent (100 mg p-dimethylamino-benzaldehyde in 1 ml concentrated hydrochloric acid diluted to 100 ml with 3 A alcohol). The approximate values are ... 

The two-emulsion (reverse) method has been used recently by Lee etal, [185] in an attempt to synthesize spherical zirconia particles under controlled conditions. In the overall scheme, a non-ionic surfactant (Span 85, Span 80, Span 40 or Arlacel 83, i.e. Sorbitan sesquioleate see below for the choice of surfactant) was dissolved in n-heptane. The HLB values of the surfactants varied in the range 1.8-6.7. Aqueous solutions of zirconium acetate or ammonia were added to two parts of the surfactant-oil phase combination the two had identical volumes. Reverse emulsions were prepared by subjecting the above to ultrasonic agitation, and the two emulsions thus produced were then mixed under stirring. The gel particles that formed in the process were separated by using a modified Dean-Stark moisture trap. Figure 4.4 presents the two-emulsion process in which the two complementary emulsions are mixed to obtain gel precipitates in the spherical droplets. 

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