. Bulletin of the British Museum (Natural History), Mineralogy. 388 THE NATURALLY OCCURRING Vauquelin (1809) experimented with the colours of chromates of lead precipitated from neutral, acid and alkaline solutions. He noted that alkaline solutions gave the reddest precipitates and also observed that an excess of lead oxide in lead chroma te gave richer reds. These prophetic observations were soon followed by a paper by P. L. Dulong (1812) who boiled a solution of potassium chromate and lead carbonate and obtained a rich red precipitate that in nitric acid turned yellow 'en cedant oxyde de plo
. Bulletin of the British Museum (Natural History), Mineralogy. 388 THE NATURALLY OCCURRING Vauquelin (1809) experimented with the colours of chromates of lead precipitated from neutral, acid and alkaline solutions. He noted that alkaline solutions gave the reddest precipitates and also observed that an excess of lead oxide in lead chroma te gave richer reds. These prophetic observations were soon followed by a paper by P. L. Dulong (1812) who boiled a solution of potassium chromate and lead carbonate and obtained a rich red precipitate that in nitric acid turned yellow 'en cedant oxyde de plomb'. J. F. L. Hausmann (1813) called crocoite 'Kallochrom' and gave a very interesting account of the Berezov chromates. Most important are his remarks on one species that he observed ; '. . ein anderes Mineral vor [kommt], welches nach meinen Versuchen chromsaures Blei zu enthalten scheint und eine genauere chemische Untersuchung verdient. Es ist theils dunkel ocherbraun, theils dunkel leberbraun ; giebt aber ein zeisiggriines Pulver. Im Bruche eben, einer Seits in das Flachmusch- liche, . . .' This is the first clear description of embreyite. This description was read with interest by Ullman (1814), who described his collection of specimens in great detail. Some of these clearly contained not only vauquelinite but phoeni- cochroite. J. L. De Bournon (1813) disagreed with Haiiy's early crystallographic data for crocoite, stating that the primitive form is a prism with angles about 85° and ^ about 108°. Probably his crystals were of totally different habit. F. Soret (1818, 1820) added new forms to the list for crocoite and in 1818 described the primitive. Fig. 2. Crocoite, Berezov ; after Soret, 1818. form as having ^ I02°5i' and a prism angle of 9i°27' ; in 1820 he gave jS I03°i6' and a prism angle of 93°. His specimens were obtained from M. Duval, 'Consul general de la Confederation Helvetique, en Russie' and M. Jurine. H. Dauber (1859, i860) gave crystallographic data
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