Kotices respecting New Books. 459 



salts must differ totally from each other, either in the na- 

 ture or proportion of their constituent parts. The primitive 

 crystal of supersiilphat of potash is an acute rhomboid of 

 74° and 106-^, the summits of which are sometimes re- 

 placed by planes perpendicular to the axis of the crystal; 

 and when this occurs at the small diagonal of the crystal, it 

 assumes the appearance of an octohedron." Mr. Phillips 

 then procured some supersiilphat of potash from Apothe-f 

 caries' Hall, which he found tasted at first sour, and red- 

 dened blue vegetable colours ; but the acid taste was soon 

 succeeded by a bitter one, and the salt evidently consisted 

 of a prismatic variety of common sulphat ni potash, mixed 

 with a considerable quantity of slender prismatic crystals, 

 which proved to be common nitre. As a proof of this, 100 

 grs. of true supersulphat saturi(ted 25 grs. of dried sub- 

 carbonat of soda ; 100 grs. of sulphat mixed with excess 

 of acid saturated only half a grain, and a similar quantity 

 of the reputed supersulphat, trom the Apothecaries' Hall, 

 saturated about one grain. Hence Mr. P. ascertained that 

 100 grs. of the salt prepared and sold under coUegial au- 

 thority for supersulphat of potash, consists of '* 58 sul- 

 phat of potash and 42 nitrat of potash. When, there- 

 fore, two drachms of this compound are exhibited, instead 

 of the like quantity of supersulphat of potash, two and a 

 half scruples of nitre are given, exceeding by a whole scru- 

 ple the largest dose mentioned by Dr. Powell." This, no 

 doubt, is wcnderfully accurate and scientific ! The College 

 chemists, and their translator, annotator, or illustrator, must 

 be considered as public benefactors in exalting the character 

 of their country for profound science and accuracy. The 

 confounding of two salts, however, which ditl'er both in 

 the quantity and the quality of their constituent parts, even 

 should it cost a few score of lives, or augment the number 

 of patients a few' thousands annually, can only be consi- 

 dered a frivolous circumstance, as perhaps not every third 

 member of t\\e College ever cast an eye on these salts, or 

 could tell what they were if laid before them on a page of 

 their Pharmacoposia. 



If colleges be doomed either to sleep or wake only to 

 blunder, it is some consolation that the present errors have 

 given occasion to verv accurate crystailographical descrip- 

 tions of several cheniical products, which have liuherto 

 been but imperfectly depicted. The "form of the primi- 

 tive crystal of su|)crtartrat of potash is a rectangular octo- 

 hedron, having two of its faces more inclined than the 

 other two ; the former meetine: at the suiimiit in an antrle 



'of 



