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68 Connection of Chemical Forces with Polarization of Light. 



Mr. Maskelyne then detailed the experiments of M. Pasteur on 

 malic and aspartic acids and asparagine, and showed how all of / 

 these could be understood to contain chemically a molecular unit 

 common to all these and perhaps to tartaric acid, and only modi- ^ 

 fied a little by the super-position as it were of other substances 

 in combination with it, upon the extremities of its molecule. 



He also dwelt on the possibility of the Paratartaric acid being 

 a quadribasic as the tartaric acid is a bibasic acid : it being on 

 this view a conjugate acid consisting ofjhe two united tartaric 

 acids. He then invited attention to the interesting nature of 

 M. Biot's investigation of the action of tartaric acid in solution in 

 water, and he showed that here the acid must be supposed capa- 

 ble of combining with an indefinite or indeed an infinite amount 

 of water, while in other eases again, bodies (such as sugar for 

 instance) exercise no effect upon the water and do not seem to 

 combine with, but only to be dissolved in it. The former is an 

 instance oi a continuous and not intermittent sort of combination : 

 and though we need not anticipate a recurrence of the contro- 

 versy of Berlhollet and Proust, yet this shows us that the actions 

 of quantity or mass so dwelt on by the former are not without a 

 great significance; and that the power that can thus enable us 

 to determine such important points in chemical statics, is well 

 worthy of the attention of the philosophic mind. 



Dr. Bence Jones permitted a Saccharimeter apparatus of SoleiFSf 

 on the double-quartz-plate principle, to be exhibited, and explained 

 its use. Mr, Tennant also exhibited a mass of quite transparent 

 Iceland spar, and a beautiful crystal of plagibedral quartz. 



Since the delivery of the lecture, a letter has been received 

 from M. Pasteur stating that he had forwarded for exhibition at 

 this lecture and in illustration of it, all the finest specimens of the 

 crystals which he has produced, which are further illustrated by 

 models and diagrams. They are the same as those which were 

 exhibited at the Academy of Sciences at Paris, and the liberality 

 of M. Pasteur's act will be appreciated by members of the Royal 

 Institution, when they are reminded that the Paratartaric acid of 

 which they are the products is impossible to be obtained, from 

 its having only once been accidentally formed, and that these 

 specimens therefore consist probably of the only large accumu- 

 lation of this body in existence. 



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