S4: ACCOUNT OF A MINERAL FROM ORKNEY. 



A. 



The gas disengaged was found bj experiment to be carbo- 

 nic acid. 



B. 



1. Tlie muriatic solution, when separated by the filter from 

 the undissolved residue, was evaporated to dryness, and cry- 

 stallised from a fresh solution in water *. The crystals were 

 slender prisms, with two of the lateral planes broader thmi the 

 rest ; were persistent in the air, and had all the chemical cha- 

 racters of muriate of strontia. Their solution was not preci- 

 pitable by ammonia, but potassa separates a portion of the 

 earth with the peculiar phenomena detailed in Dr Hope's va- 

 luable paper in volume iv. Phil. Trans. Edin. 



2. The nitric solutions gave small brilliant crystalline flakes ; 

 and these were also formed on the addition of nitric acid to 

 the muriatic solution, but were speedily dissolved on the addi- 

 tion of water. 



3. In order to satisfy myself still farther that the muriatic 

 salt had a base of strontia, a very dilute solution of sulphate of 

 soda was dropt into a concentrated muriatic solution of the mi- 

 neral ; but no precipitate was formed : when the sulphate was 

 less diluted, a precipitate fell, though less copious than when 

 added to a similar solution of muriate of barytes, but more 

 abundant than with muriate of lime. 



4. After separating, by successive crystallizations, the cry- 

 stals from the muriatic solution, a small quantity of an acrid 



and 



* The first addition of water caused a considerable evolution of caloric. 



