332 Biographical Account of [Nov* 



moting the crystallization of alum with potash. Soda and lime 

 he found possessed no efficacy whatever. It is rather surprising 

 that this did not lead him to the true conclusion, that there are 

 two species of alum, one containing potash, and the other 

 ammonia. This conclusion was first drawn by Vauquelin. 

 Whether the analysis of alum by Berzelius, which is commonly 

 received, be correct, is a point that I rather believe will require 

 some further examination. The subject is of importance, 

 because the weight of an atom of alumina, and even the mode of 

 manufacturing alum, must be a good deal influenced by it. 



6. On Antimoniated Tartar. — This is the name by which 

 Bergman distinguished tartar emetic, the only antimonial prepa- 

 ration much used in medicine. This dissertation is of consider- 

 able importance. He details the different processes given for 

 preparing this salt, and shows that they were so discordant and 

 inaccurate, that the same substance could not be obtained at 

 different times. His process is to mix powder of algaroth (the 

 white powder which precipitates when chloride of antimony is 

 mixed with water) with cream of tartar, to boil the mixture for 

 half an hour in water, then to pour off the liquid, evaporate to a 

 pellicle, and crystallize. It is now known that tartar emetic is 

 a salt composed of bitartrate of potash (which acts the part of an 

 acid) and protoxide of antimony. 



7. On Magnesia. — This dissertation, first published in 1775, 

 may be considered as the third chemical dissertation on magnesia. 

 The first was by Dr. Black, in 1755 ; and the second, by Mar- 

 graf, in 1759. Bergman describes the method of obtaining 

 magnesia, details its properties, and gives a pretty full account 

 of the salts which it forms with the different acids. The only 

 paper of much consequence which has made its appearance upon 

 magnesia since Bergman's paper, is a small book published by 

 Butini, of Geneva, in 1781, entitled " Nouvelles Observations 

 et Becherches Analytiques sur la Magnesie du Sal d'Epsom." 

 But most of the magnesian salts have been analyzed with toler- 

 able accuracy by modern chemists . 



8. On the Forms of Crystals. — This paper was first published 

 in 1773, and is remarkable, because it contains the very same 

 discovery which afterwards led Haiiy to his theory of crystals. 

 He shows that the primitive form of calcareous spar is a rhom- 

 boid, the faces of which have angles of IOI4- and 78^°, that all 

 the different crystals of calcareous spar may be formed upon such 

 a base, and that a nucleus having the primitive form may be 

 extricated mechanically from all the different forms. In short, 

 this curious paper, which he informs us was the fruit of many 

 years' assiduous observations on crystals, maybe considered as 

 exhibiting the first outline of Haiiy's theory. 



9. On Siliceous Earth. — This paper was published in 1779. 

 Bergman in it states with precision the chemical characters of 

 silica, shows that it differs in its properties from the other earths > 



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