COMPLETE ANALYSIS. 49 



reductor used is practically the same as the simple device described l.y Sliimt-r." 

 The tube has an internal diameter of three-eighths ,f an inch, and is L'II inches Ion-. 

 It is drawn out ami cut off at its lower extremity with an opening of 1 mm diam- 

 eter. One inch of coarse sand is placed at the bottom and tin- rest <.l" thetnhe is 

 tilled with amalgamated /inc. The ordinary I*, ami A "iron I'ree " Lrranulated /inc 

 is moistened with dilute sulphuric acid and a little clear mercury stirred in. Suction 

 is applied and regulated so that <>0 CC of solution passes through the reductor in 

 five minutes. The washing is allowed to proceed more rapidly. I'.lanks are run to 

 determine the constant correction for the reductor. 



TlTAMIM. 



To looccof solution A, in a porcelain evaporating dish, 10 cc of strong sulphuric 

 acid is added and the solution evaporated on the steam bath until the hydrochloric 

 acid is expelled and the sulphuric acid solution has little or no yellow color. After 

 slight dilution the solution is filtered into a 100 cc graduated cylinder, 2 cc of pure 

 ;> per cent hydrogen peroxid h added, and the solution diluted to 50 cc. In another 

 graduated cylinder containing about 40 cc of water, 2ccof 3 per cent peroxid is added 

 and then gradually a standard solution of titanium run in from a burette until the 

 colorsmatch, when thesolutions are looked at through the samedepth of column. The 

 standard solution used in this laboratory is made up so that 1 cc equals 0.0002 gram 

 of titanium oxid (TiO 2 ). The standard is made up by roughly weighing out some- 

 what more than the right amount of some titanium salt or compound, and after 

 getting it into solution standardizing it by gravimetric analysis, subsequent dilution, 

 and reanalysis. 



PHOSPHORIC ACID. 



The volumetric method based upon that adopted by the Association of Official 

 Agricultural Chemists is used for the determination of phosphoric acid. The fol- 

 lowing solutions are prepared: 



PREPARATION OF REAGENTS. 



(1) Molybdic solution. One hundred grams of molybdic acid are dissolved in 417 

 cc of ammonia, specific gravity 0.96, and the solution thus obtained poured into 

 1,250 cc of nitric acid, specific gravity 1.20. The flask in which the mixture is made 

 is kept cool by immersion in water until the reaction is completed. The mixture is 

 kept in a warm place for several days, until a portion heated to 40 C. deposits no 

 yellow precipitate, when the solution is decanted and preserved in a glass-stoppered 

 bottle. 



(2) Standard potassium hydroxid solution. This solution is made up to contain 3.6342 

 grams of potassium hydroxid to the liter. It is prepared by diluting <i4.7<> cc of 

 normal potassium hydroxid, which has been freed from carbonates to 1 liter. One 

 cubic centimeter is equal to 0.2 mg of phosphoric acid (P 2 O 5 ). 



(3) Standard nitric acid solution. The strength of this solution is the same a* the 

 standard alkali solution, and is determined by titrating against that solution, using 

 phenolphthalein as indicator. 



(4) Phenoljilitluik'in volution. One gram of phenolphthalein is dissolved in 100 cc 

 of alcohol. 



Jour. Amer. Chem. Soc., 21: 723. 



& Mere traces of hydrofluoric acid, either in the peroxid or the titanium solution, 

 render this method inexact, hence care should be exercised as to the character of the 

 peroxid, which, as sold in the market, often contains fluorin. (Hillebrand, Bui. 

 U. S. Geol. Sur. 176, p. 68. ) 



6090 No. 7903 J- 



