408 Miscellaneous Intelligence. 



the rapid decay and change of cast iron is partly to be attri- 

 buted to a galvanic action, the plumbaginous crust in contact 

 of the cast metal producing an electro-motive combination, aided 

 by and promoting: the decomposition of the sea water, and of 

 its saline contents. Considering the resemblance of this crust 

 to that described by Mr. Daniell, as produced by the action of 

 acids upon cast iron, (see Vol. II., p. 233, of this Journal), I ex- 

 pected to detect a portion of silica in it, but was disappointed. 



2. Solubility of Magnesia, Q,nd its Carbonate in Water. — Dr. 

 Fyfe has lately experimented on the solution of magnesia and 

 its carbonate in water ; and not only finds that these substaiices 

 are soluble, but also that,, as with lime, they are more soluble 

 in cold than in hot water. The magnesia was prepared by pre- 

 cipitation, washing, and ignition ; water was then digested on it, 

 and afterwards the magnesia, dissolved in the water, separated 

 by carbonate of ammonia and phosphate of soda. In this 

 way it was ascertained, that 1 part of magnesia required 

 5142 parts of water, at a temperature of 60°, to dissolve it; 

 and at a temperature of 212°, 36000 parts of water. The effect 

 of temperature is so great in altering the solubility of mag- 

 nesia in water, that if a cold saturated solution be heated in a 

 narrow-necked matrass, it becomes turbid on rising to 212°. 



On repeating the experiments with carbonate of magnesia, it 

 was found that 1 part required 2493 parts of water, at the tem- 

 perature of 60°, for its solution, and 9000 parts, at the boiling- 

 point. — Edinburgh Journal, vol. v., p. 305. 



3. On the Solution of Carbonate of Lime, by Mr. Dalton. — Mr. 

 Dalton, in a paper containing remarks on the analysis of spring 

 and mineral waters, has stated some interesting circumstances 

 respecting the alkaline properties of solution of carbonate of 

 lime. It is stated, " that all spring water containing carbonate 

 or super-carbonate of lime, is essentially limy or alkaline, by 

 the colour tests. And this alkalinity is not destroyed till some 

 more powerful acid, such as the sulphuric or muriatic, is added, 

 sufficient to saturate the whole of the lime. Indeed, these acids 

 may be considered as sufficient for tests of the quantity of lime 

 in such waters ; and nothing more is required than to mark the 

 quantity of acid necessary to neutralize the lime. It does not 

 signify whether the water is boiled or unboiled, nor whether it 

 contains sulphatr of lime along with the carbonate ; it is still 

 limy in proportion to the quantity of carbonate of lime it con- 

 tains. Agreeably to this idea, too, I find that the metallic 

 oxides, as those of iron or copper, are thrown down by common 

 spring Avater, just the same as by free lime. Notwithstanding, 

 this carbonate of lime, in solution in water, contains twice the 

 acid that chalk or limestone does. I fully expected 'the super- 



