AGRICULTURAL ANALYSIS 



The most concentrated aqueous acid has a specific gravity of 

 1.65, is colorless, fumes slightly when exposed to the air, and 

 boils at 200. It has no odor, possesses an oily consistence and 

 has a strong and agreeably acid taste. It reddens litmus with- 

 out bleaching it and is slowly volatilized at 138 without decom- 

 position. It is unaffected by exposure to the light, even the 

 sun's rays. It is not decomposed by hydrosulfuric, sulfurous, 

 or hydrochloric acids, nor by alcohol. Paper saturated with the 

 strong acid does not take fire spontaneously, but it deflagrates 

 with red-hot charcoal. 



The acid prepared by the method of Kreider has approxi- 

 mately the composition of the di-hydrate, HC1O 4 .2H 2 O. It is 

 usually a little more dilute than is shown by the above formula. 

 The di-hydrate is quite stable and the more dilute acid can be 

 kept for an indefinite time. Kreider has kept the acid for six 

 months and noticed no -change whatever in its composition. Acid 

 containing one gram of perchloric acid in a cubic centimeter 

 has been kept three months with perfect safety. There is no 

 reason why the strong aqueous acid should not be made a reg- 

 ular article of commerce by dealers in chemical supplies, under 

 proper restrictions for storage and transportation. 



The strong acid made in the laboratory of the Bureau of 

 Chemistry by the Kreider method has not given the least indi- 

 cation of easy or spontaneous decomposition. 



492. The Analytical Process. The perchlorate process can- 

 not be applied in the presence of sulfuric acid or dissolved sul- 

 fates. This acid, when present, is to be removed by the usual 

 methods before applying the perchloric acid. Phosphoric acid 

 may be present, but in this case a considerable excess of the re- 

 agent must be used. The process, as originally proposed by Cas- 

 pari and carried out by Kreider is as follows : OT 



The substance, free from sulfuric acid, is evaporated for the 

 expulsion of free hydrochloric acid, the residue stirred with 20 

 cubic centimeters of hot water and then treated with perchloric 

 acid, in quantity not less than one and one-half times that re- 

 quired by the bases present, evaporated, with frequent stirring, 

 67 American Journal of Science, 1895, 149 : 446. 



