58 On the Analysis of 
sulphuric acid, either free or combined, these 
are the best tests. ‘The sulphate of barytes is 
perhaps the most insoluble salt known. Even 
rain water collected from slated houses, though 
softer than spring or river water, exhibits by 
these tests 1 grain of sulphuric acid in 20 or 
30 thousand grains. 
5. Oxalic acid test. When the object is to 
obtain the lime, either free or combined, in 
any water, this is the best test. It may be 
proper to add a little ammonia in some cases 
of combined lime. The oxalate of lime slowly 
precipitates in the state of an insoluble salt. 
The quantity of lime may be ascertained, 
either by collecting the precipitate, or by care- 
fully and gradually adding the due quantity of 
acid and’no more, when ‘the strength of ‘the 
acid has been ‘previously ascertained. 
6. Nitrates of silver'andmercury tests. These 
are'tests of muriatic acid or of muriates; the 
muriates of silver and: mercury are formed, 
both insoluble salts. It does not often happen 
that ‘spring waters contain notable propor- 
tions of the muriatic acid either free or com- 
bined. 
7. Sulphuretted hydrogen water and hydro- 
sulphurets. 'These are excellent tests for lead, 
mercury ‘and several metals, giving peculiar 
insoluble precipitates of the ‘sulphurets .of 
