Hartley — On the Composiiion of two Hard- Water Deposits. 45 



Analysis of a Crystalline Stony Deposit from Hard Water, 

 Dublin. 



This analysis was made in my laboratory in 1887, by Mr. John 

 E. Purvis, Associate of the Royal College of Science, Associate of 

 the Institute of Chemistry. 



It happened that at the time this water deposit was in course 

 of formation the canal water was being analysed in my labora- 

 tory at the commencement of every month, and the analyses were 

 published in the Eeport of the Registrar- Greneral for Ireland. 

 Though the canal water was supplied to the Eathmines Town- 

 ship at that time, it did not differ materially from that in the 

 canal at other places nearer town as far as the dissolved con- 

 stituents were concerned. This was shown by analyses made 

 at the time, and it is the matter in solution only which is 

 analysed, and which is concerned in forming these deposits. It 

 is true that the small amount of suspended organic matter is 

 carried down along with the mineral constituents, but it is more 

 especially the amount of mineral matter in solution which is 

 capable of being precipitated upon the removal of carbonic acid^ 

 to which I draw attention, and this is shown in the, accompanying 

 analyses by the total solid impurity and the temporary hardness, 

 or that amount of solid matter which can be removed by boiling 

 100,000 parts of the water. 



