SELECTED ARTICLES. 
37 
unite with 32.5 of chlorine, and that97.26 of chlorine absorb 
2.74 of hydrogen gas, to form 100 parts of hydrochloric 
acid. 
Method of recognising the presence of nitric acid in vinegar. 
The falsification of vinegar by nitric acid is very rare, it is 
detected in the following manner; the vinegar is saturated 
with the carbonate of potassa, which is then evaporated to ob- 
tain a salt. When the salt is obtained in the dry state, an ex- 
amination is made to ascertain whether it contains a nitrate: 
1. by throwing a small quantity upon live coals; if nitrate of 
potassa is present, partial deflagration will ensue; 2. by treat- 
ing this salt mixed with brass filings with sulphuric acid; if it 
contains a nitrate, reddish vapours are disengaged with the 
strong odour of nitrous acid, which is not the case if the salt 
obtained contains no nitrate.* 
Method of testing vinegar mixed with oxalic or tartaric 
acids. 
These sophistications which are scarcely now met with, can 
nevertheless be determined, 1. by the evaporation of the vine- 
gar, which, when it contains these acids, leaves a crystalline re- 
siduum, a residuum which should be afterwards examined; 2. 
because vinegar thus adulterated, evaporated to two-thirds, and 
then poured into a solution of potassa, occasions a granular 
crystalline precipitate of the oxalate or the tartrate of po- 
tassa, which is not obtained when the vinegar does not con- 
tain these acids. 
Method of recognising the alteration of vinegar by acrid 
substances. 
The addition of acrid substances to vinegar is of ancient 
* We have been assured that the vinegar makers have augmented 
their product by sulphuric acid containing nitric acid; we have never met 
with vinegar thus falsified, but we know that for some time, the sulphuric 
acid of commerce has contained a small quantity of nitric acid, arising 
from a new method of preparing it. 
