Building Stones of Victoria. 185 



At the end of the time the cubes were carefully removed, 

 dried for many hours at 110 degrees C, and then weighed, the 

 difference between the two weights being due to the action of 

 the carbonated water. 



All the stones, with the exception of those from Barrabool 

 Hills and Apollo Bay, lost weight. The Darley stone, known to 

 contain a large percentage of carbonate, lost as much as 2 per 

 cent., while the marble lost 1.8 per cent. In the case of the 

 Darley sandstone, one is dealing with a porous stone, where 

 the solution can percolate all through, while with the marble, 

 which has a very low absorption (.18 per cent, by weight) the 

 action is almost entirely confined to the surface. The Darley 

 stone also lost some weight through some of the grains falling 

 away, when the cement was weakened by the solution of the 

 carbonate. The action on the marble was sufficient to remove a 

 film nearly .2 mm. in thickness from the whole surface of the 

 stone, with the exception of the thin carbonaceous veins, which 

 stood out as ridges. The effect on the Apollo Bay stone was 

 to give it a lighter colour, much the same as is produced by a 

 few years' weathering. With regard to the other stones little 

 or no change was noticeable in appearance. The amounts lost 

 by the Sydney, Dunkeld, Stawell and Egerton stones is scarcely 

 appreciable, whereas the marble, Bacchus Marsh and Darley 

 stones all lost considerable amounts, due to the carbonates 

 therein. The increase in weight of the Barrabool Hills and 

 Apollo Bay stones is probably due to the presence of ferrous 

 iron in the stones, which becomes oxidised. 



Table of Percentage Losses by Corrosion. 



stone Weiafht lost in percentage 



Stawell - - - - 0.06 



Dunkeld - - - - 0.01 



Barrabool Hills - - - 0.17^ 



Apollo Bay - - - 0.15* 



Bacchus Marsh - - - 0.38 



Darley - - . . 2.01 



Egerton (tine) - - - 0.00 



Egerton (coarse) - - - 0.02 



Carrara Marble - - - 1.79 



Sydney - - - 0.03 



* Denotes Percentage gained. 



