74 METHODS OF ANALYSIS [Chap. 



(b) 04% sodium hydroxid solution. 



(C) N /W sulphuric acid. — One cc. is equivalent to 16.22 mg. of nicotin. 



(d) Phenacetolin solution. — Prepare a 0.5% alcoholic solution. 



(e) Cochineal solution. — Prepare as directed under I, 16 (k). 



61 DETERMINATION. 



Weigh 5-6 grams of tobacco extract, or 20 grams of finely powdered tobacco 

 which has been previously dried at 60°C. if necessary, into a small beaker. Add 

 10 cc. of the alcoholic sodium hydroxid and follow, in the case of tobacco extract, 

 with enough pure powdered calcium carbonate to form a moist but not lumpy mass. 

 Mix thoroughly, transfer to a Soxhlet extractor and exhaust for about 5 hours with 

 ether. Evaporate the ether at a low temperature, and take up the residue with 50 

 cc. of the 0.4% sodium hydroxid solution. Transfer this residue by means of water 

 to a 500 cc. Kjeldahl flask, and distil with steam, passing the distillate through a 

 condenser cooled by a rapidly flowing current of water. Use a 3-bend outflow tube, 

 and, to prevent bumping and frothing, add a few pieces of pumice, and a small piece 

 of paraffin. Distil till all the nicotin has passed over, the distillate usually varying 

 from 400-500 cc. When completed, only about 15 cc. of the liquid should remain in 

 the flask. Titrate the distillate with N/10 sulphuric acid, using the phenacetolin 

 or cochineal solution as indicator. 



Silicotungstic Acid Method.^^ — Official. 



62 REAGENTS. 



(a) Silicotungstic acid solution. — Prepare a 12% solution of the silicotungstic 

 acid having the following formula: 4H20.Si02.12W03.22H20. 



(b) Sodium or potassium hydroxid solution [1 to 2). 

 (C) Dilute hydrochloric acid {1 to 4) • 



63 DETERMINATION. 



Weigh such an amount of the preparation as will contain preferably between 0.1 

 and 1.0 gram of nicotin (if the sample contains very little nicotin, about 0.1%, do 

 not increase the amount to the point where it interferes with the distillation) ; wash 

 with water into a500cc. round-bottomed distillation flask; add a little paraffin to pre- 

 vent frothing, a few small pieces of pumice and a slight excess of the sodium or 

 potassium hydroxid, using phenolphthalein as an indicator. Distil rapidly in a 

 current of steam through a well-cooled condenser, connected by means of an adapter 

 with a suitable flask containing 10 cc. of the dilute hydrochloric acid. When distil- 

 lation is well underway, heat the distillation flask to reduce the volume of the liquid 

 as far as practicable without bumping or undue separation of insoluble matter. Dis- 

 til until a few cc. of the distillate show no cloud or opalescence when treated with a 

 drop of the silicotungstic acid and a drop of the dilute hydrochloric acid. Confirm 

 the alkalinity of the residue in the distillation flask with phenolphthalein solution. 

 Make up the distillate, which may amount to 1000-1500 cc, to a convenient volume (the 

 solution may be concentrated on the steam bath without loss of nicotin), mix well 

 and pass through a large dry filter if not clear. Test a portion with methyl orange 

 to assure its acidity. Pipette an aliquot, containing about 0.1 gram of nicotin, into 

 a beaker lif the samples contain very small amounts of nicotin, an aliquot contain- 

 ing as little as 0.01 gram of nicotin may be used), add to each 100 cc. of liquid 3 cc. 

 of the dilute hydrochloric acid, or more if the necessity is indicated by the test with 

 methyl orange, and add 1 cc. of the silicotungstic acid for each 0.01 gram of nico- 



