BENZOIC ACID. 71 



deposited on the cool parts of the glass. The aro- 

 matic smelling vapour causes much coughing when 

 inhaled in small quantity. 



5. Heat a small portion with concentrated sulphuric 

 acid and observe that no blackening ensues. 



6. Neutralise its hot watery solution with baryum 

 carbonate, and evaporate solution of baryum benzoate 

 to crystallisation. 



7. Add to the solution of this or any other benzoate 

 some neutral solution of ferric chloride, and observe the 

 precipitation of a buff- coloured precipitate of almost 

 insoluble ferric benzoate. For diagnosis of this preci- 

 pitate from succinate, see Succinic acid, 4. 



8. To a solution of a benzoate or of benzoic acid add 

 some cupric acetate and warm ; a blue precipitate of 

 rather insoluble basic benzoate of copper will be formed. 



. Qualitative and systematic analysis. 1. Col- 

 lect the bile from the gall-bladders of dead persons or 

 animals, or from biliary fistulas of the latter produced 

 by art. Observe its colour, formed or crystalline 

 ingredients if any, and its reaction, which should in 

 health be neutral or feebly alkaline. 



2. Add to a filtered portion a little acid, and, if ne- 

 cessary, filter again. Then heat gently to boiling, and if 

 any precipitate ensues albumen is present. 



3. Mix the bile with five or six volumes of absolute 

 alcohol, and let stand; filter from the precipitated 

 mucus and cholesterine (and albumen if such was 

 abnormally present). Evaporate the solution to dry- 

 ness, and use the residue as purified bile. 



