302 SALTS 



1 atom carbonic acid 2-75 

 1 atom magnesia 2-5 



3 atoms water 3-375 



8-625 * 



I find that this artificial carbonate becomes an- 

 hydrous by simple exposure to the air, and falls 

 down into powder. 



Hydrate, 4 Hydrate of magnesia. This beautiful min- 

 eral is obviously analogous to a salt. It was 

 first discovered by Dr. Bruce in the serpentine 

 at Hoboken in New Jersey ; more lately, mag- 

 nificent specimens have been detected in the 

 Shetland Islands by Dr. Hibbert I believe, in 

 the serpentine of the island of Unst. It has a 

 beautiful snow white colour, sometimes with a 

 shade of green ; a pearly lustre ; is composed 

 of thin semitransparent folia, and has a specific 

 gravity of M3. Its constituents, according to 

 the analysis of Strom eyer which I repeated with 

 scarcely any difference in the result, are 



1 atom water . . 1*125 



1 atom magnesia . . 2 '5 



Water .... 0-00546 



Oxides of iron and manganese 0-00762 



The small excess of water was probably com- 

 bined with the oxides of iron and manganese 

 present in the mineral. The whole of the fo- 



* Afhandlingar, VI. 21. 



