39 AGRICULTURAL ANALYSIS 



only be used when it is certain that no organic nitrogen is present. 

 The ammonia is collected in set sulfuric acid, and, as an indicator, 

 it is recommended to use paranitro-phenol solution in the pro- 

 portion of one to 10 of alcohol. Tincture of cochineal or congo 

 red in water is also permitted. 



Organic Nitrogen. The method of Kjeldahl, with its modern 

 modification for the inclusion of nitric nitrogen, is recommended. 



342. Estimation of Perchlorate in Chile Saltpeter. Attention 

 is called to the occasional occurrence in Chile saltpeter of 

 potassium perchlorate. The method employed depends upon the 

 determination of the chlorin content of the material under inves- 

 tigation both before and after the decomposition of the perchlo- 

 rate. The conversion of perchlorate of potassium is secured by 

 simple ignition or by ignition after the addition of different re- 

 agents, as, for instance, metallic lead, caustic lime, sodium car- 

 bonate, magnesium oxid, etc. The following method is recom- 

 mended as satisfactory and easily carried out. 36 



In this method five grams of Chile saltpeter, in which the 

 amount of chlorin has been determined, is placed in a porcelain 

 crucible of about 40 to 50 cubic centimeters capacity with from 

 15 to 20 grams of lead borings and submitted to a gradually in- 

 creased heat. When the salt and the lead are melted, the mass 

 is vigorously stirred with a copper wire with a regulation of the 

 heat so as not to secure a too rapid evaporation of the mass. 

 When the mass begins to thicken and only a few bubbles of gas 

 are escaping, the heat is raised to a dark red on the bottom of 

 the crucible and held at this temperature for one or two minutes. 

 After cooling, the melt, which now contains nitrate and chlorate, 

 is softened with hot water and washed into a beaker. Three or 

 four grams of carbonate of soda are added and the mixture 

 gradually warmed. After filtration nitric acid is added to the 

 filtrate to acidity, and the chlorin estimated in the usual way with 

 the nitrate of silver. 



From the amount of chlorin obtained, that which was originally 

 present is subtracted and the difference is the chlorin due to 

 * Selckmann, Zeitschrift fur angewandte Chemie, 1898, 11 : 101. 



