INVESTIGATIONS OF BECK 437 



conducted through a tank supplied with a current of cold water. 

 The ends of the tubes should not dip below the surface of the 

 liquid in the receivers. When the condensed liquid collects in 

 considerable quantities in the safety tube the lamp should be 

 extinguished under the flask, which permits the return of the 

 liquid to the flask by means of the siphon. This should be done 

 two or three times during the progress of the distillation to pre- 

 vent a too high concentration of the soda-lye, thus endangering the 

 flask. The excess of the acid in the receiver is determined by 

 titration, as in the regular kjeldahl method. Blank determina- 

 tions are made, from time to time, and corrections made in har- 

 mony therewith. 



377. Investigations of Beck. A late contribution to the 

 analysis of Chile saltpeter is that of Beck. 59 



Beck examined the direct method of Ulsch, subsequently de- 

 scribed, and the indirect method which is so commonly em- 

 ployed by dealers, depending on the determination of the other 

 principal ingredients and subtracting this from 100 to get the per 

 cent, of nitrate of soda in the mixture. This last method is par- 

 ticularly unsatisfactory, since it gives 1.5 per cent, of sodium ni- 

 trate too much. The quantity of perchlorate which is present is 

 also important and for technical purposes, such as the nitration 

 of cellulose, etc., it is recommended not to use any sample which 

 yields more than one per cent, of a sodium salt due to perchlorate. 



Beck expresses the hope that the producers of Chile saltpeter 

 in the future will cease to urge the use of the indirect method 

 and will refrain from attacking the validity of the direct methods, 

 and calls attention to the fact that the increasing possibility of 

 producing nitric acid and nitrates directly from the atmosphere 

 may supersede the necessity of using the natural salt. 



The factors for calculating the percentage of nitric acid when 

 it is reduced to ammonia may be based upon the number of cubic 

 centimeters of half-normal suifuric acid required for 10 cubic 

 centimeters of a solution containing 33 grams of sodium nitrate in 

 one liter. The factors are as follows: 



w Zeitschrift fur analytische Chemie, 1906, 45 : 669. 



