25 



The volumetric silver nitrate method for determining cyanogen in 

 potassium cyanid was adopted as official (using N/20 instead of N/10 

 solution of silver nitrate) : 



POTASSIUM CYANID. 



CYANOGEN (OFFICIAL). 

 SOLUTION REQUIRED. 

 A twentieth-normal solution of silver nitrate. 



METHOD. 



A large quantity of the sample is weighed out in a weighing bottle, dissolved in water, 

 and made up to a definite volume. Aliquot portions of this are taken for analysis. The 

 twentieth-normal silver nitrate solution is added a drop at a time with constant stirring, 

 until one drop produces a permanent turbidity. In calculating the results, one equivalent 

 of silver is equal to two equivalents of cyanogen, according to the following equation: 



2 KCN + AgNO 3 = KCN.AgCN + KNO 3 . 

 The Kissling method of determining nicotin was adopted as official : 



TOBACCO AND TOBACCO EXTRACTS. 

 NICOTIN, METHOD I (OFFICIAL). 



SOLUTIONS REQUIRED. 



An alcoholic soda solution containing 6 grams of sodium hydroxid, 40 cc of water, and 60 

 cc of 90 per cent alcohol. A weak sodium hydroxid solution containing 4 grams of sodium 

 hydroxid in 1,000 cc of water. A standard sulphuric acid solution. 



METHOD. 



About 5 to 6 grams of tobacco extract or 20 grams of finely powdered tobacco, which has 

 been previously dried at 60 C, so as to allow it to be powdered, is weighed out in a small 

 beaker. Ten cubic centimeters of the alcoholic soda solution is added, followed, in the case 

 of the tobacco extract, with enough C.*P. powdered calcium carbonate to form a moist but 

 not lumpy mass. The whole is well mixed. This is transferred to a Soxhlet extractor and 

 exhausted for about 5 hours with ether. The ether is evaporated off at a low temperature by 

 being held over the steam bath, and the residue is taken up with 50 cc of the weak soda 

 solution mentioned above under "solutions required." This is transferred by means of water 

 to a Kjeldahl flask, capable of holding about 500 cc, and distilled in a current of steam, using 

 a condenser through which water is flowing rapidly. A three-bend outflow tube is used, and 

 a few pieces of pumice and a small piece of paraffin are added to prevent bumping and froth- 

 ing. The distillation is continued till all the nicotin has passed over, the distillate usually 

 varying from 400 to 500 cc. When the distillation is complete only about 15 cc of the liquid 

 should remain in the distillation flask. The distillate is titrated with standard sulphuric 

 acid, using phenacetolin or cochineal as indicator. One molecule of sulphuric acid is 

 equivalent to two molecules of nicotin. 



