WATER OF THE IRISH SEA. 291 



II. Estimation of the Sulphuric Acid, as Barium Sulphate. 





Water taken. 



BaS04 obtained. 



SO4 in 1000 





grams. 





grams. 



I. 



... 102*272 



0-6447 



2-5972 



II. 



. .. IOO'2o6 



o"6295 



2-5884 



Mean 2'5928 



In the older analyses^ the sulphuric acid was calculated 

 as SO3 : the above number reduced to the amount corre- 

 sponding to this formula is 2*16075. Probably no con- 

 stituent of sea- water is subject to greater variations in 

 amount than the sulphuric acid. This may be due to 

 several causes^ among which may be enumerated (i) the 

 varying amounts of sulphates brought down by rivers,, and 

 (2) the fact that the sulphuric acid contained in sea-water 

 is frequently reduced in the presence of organic matter to 

 sulphuretted hydrogen"^. The variation in the Atlantic^ ac- 

 cording to Forchhammer^ may amount to 0*0145 per cent, 

 (max. 0'2436 per cent., min. 0*2289 P^^ cent.) . The mini- 

 mum quantity, it will be observed, somewhat exceeds that 

 found in the water of the Irish Channel, again showing 

 the influence of the influx of fresh water from the rivers. 

 The water of the English Channel, according to Bischof, 

 contains a similar amount of SO3, viz. 0*2141 per cent., 

 with which our result agrees perfectly. 



III. Determination of the Total Amount of Lime. 



We found some little difliculty at the outset in exactly 

 determining the proportion of this constituent by the ordi- 

 nary method of separation, owing to the facility with which 

 varying quantities of magnesia coprecipitate with the cal- 

 cium oxalate. By repeatedly dissolving the mixed oxalates 

 in hydrochloric acid, and reprecipitating the calcium salt 

 by the addition of ammonia and a few drops of ammonium 

 oxalate, we at length obtained it perfectly free from ad- 



* See Hayes, Sillim. Americ. Journ. March 1851, p. 241. 



U2 



