3. Filter and wash with alcohol. ¦ ¦ ¦---------------------------------------¦ ¦ ¦ ¦ ¦ FILTRATE RESIDUE ¦ ¦ ¦ ¦ may contain barium propionate, may contain barium acetate, barium butyrate. barium formate, barium benzoate. ¦ ¦ ¦ ¦ 1. Evaporate to dryness. 1. Evaporate off alcohol and dissolve up the residue on 2. Dissolve residue in 150 the filter in hot water and c.c. water. neutralise. 3. Acidify with phosphoric 2. Divide the solution into acid and distil. four portions: 4. Saturate distillate with (a) Add ferric chloride solution. calcium chloride and distill over a few c.c. ~Brown~ colour = _acetic_ or _formic_ acids. 5. Test distillate for butyric acid: ~Buff ppt.~ = _benzoic_ acid (see ether soluble acids). Add 3 c.c. alcohol and 4 drops concentrated sulphuric acid. (b) Add silver nitrate solution; then add one drop ~Smell of pineapple~ = _butyric_ ammonia water, and boil. acid. ~Black~ precipitate of metallic Propionic acid in small silver = _formic_ acid. quantities cannot be distinguished from butyric (c) Evaporate to dryness; mix acid by tests within the with equal quantity of scope of the bacteriological arsenious oxide and heat laboratory. on platinum foil. Unpleasant ~smell of cacodyl~ = _acetic_ acid. (d) Add a few drops of mercuric chloride solution in test-tube, and heat to 70° C. ~Precipitate~ of mercurous chloride which is slowly reduced to mercury = _formic_ acid.