302 Aiialyses of Books. [April, 



sition of the hyiliiodate and iodate of magnesia when ihey reach a 

 certain point of concentration, but it is much more marked with 

 magnesia. 



The flea-coloured matter is decomposed when put upon burning 

 eoals. Iodine is disengaged, and magnesia remains. Potasli de- 

 composes it hkewise. When boiled in water, its colour is not 

 changed, but the liquid is found to contain a little iodate and 

 hydriodate. If the quantity of water be considerable, pure mag- 

 nesia remains, and the water contains iodate and hydriodate. 



From tliese facts it appears that the flea-coloured matter is an 

 ioduret of magnesia, and that its existence in water depends upon 

 the property which the iodate and hydriodate of magnesia have of 

 muiu^illy decomposing each other when concentrated to a certain 

 point. When the water is in great quantity, no ioduret of mag- 

 nesia appears ; but it is deposited as the concentration advances. 



This phenomenon does 'not take place with the iodates and hy- 

 driodates of potash and soda. It begins to show itself with those of 

 strontian. It becomes more sensible with the iodate and hydriodate 

 of lime, and is very conspicuous with those of magnesia. But this 

 last alkaline basis has a weaker affinity than the others ,• and it is 

 perhaps because the oxides of zinc and iron, &c. have a still 

 weaker, that they do not condense a sufficient quantity of hydriodic 

 and iodic acids to prevent them from acting on each other, and that 

 in treating them with iodine no iodates and hydriodates are formed, 

 though these salts may be obtained separately. 



(To be, conlinucd.) 



Article X. 

 Analyses of Books. 



An Attempt io estalltsh a pure scientific System of Mineralogy 

 ly the Application of the Electro-Chemical Theory, and the Che- 

 mical Proportions. > By J. .Jacob Berzellus, M. D. F. R. S. Pro- 

 fessor of Chemistry at Stockholm. Translated from the Sivedisk 

 Original by John Black. 1814. 



TtiE doctrine of chemical proportions, though hut recently 

 introduced into chemistry, has produced a great reform in the 

 science, and has given birth to a degree of accuracy, both in cx])e- 

 rimenting and reasoning, which has already placed chemistry on a 

 footing with tlie mathematical sciences. Nobody has contributed 

 more to jjroduce this reform than Professor Berzelius. He has 

 made the mo^^r numerous and accurate analyses which we at present 

 possess, and lias pointed out several general conclusions, which 

 serve greatly to facilitate this kind of investigation. His activity, 

 which surpasses that of any other chemical experimenter of the 



