PARIS GREEN 629 



carbonate and approximately 100 cubic centimeters of water; 

 cool, add hydrochloric acid until acid, and then sodium bicar- 

 bonate until alkaline; make up to the mark and titrate aliquots 

 of 50 cubic centimeters with iodin solution as in Method I. 



(b) Sodium acetate solution. Dissolve 12.5 grams of the 

 crystallized salt in each 25 cubic centimeters. 



(c) Sodium potassium tartrate solution. Dissolve from two 

 to three grams of sodium potassium tartrate in each 50 cubic 

 centimeters. 



(d) Slarch solution. Prepare a starch solution as in Method I. 

 Determination. Place one gram of paris green in a 100 cubic 



centimeter flask and boil for five minutes with 25 cubic centi- 

 meters of the sodium acetate solution. Make to the mark, shake, 

 and pass through a dry asbestos gooch filter. Use an aliquot 

 of this filtrate for the determination of the soluble arsenious oxid 

 by means of the iodin solution. Transfer the residue on the 

 filter to a beaker, beat up with a little water, dissolve in con- 

 centrated hydrochloric acid adding a drop at a time, then add 

 three or four drops in excess. Transfer the whole to the 100 

 cubic centimeter flask originally employed and analyze aliquots 

 of from 20 to 40 cubic centimeters. Add concentrated sodium 

 carbonate solution, a drop at a time, to each of these aliquots un- 

 til a slight permanent precipitate is formed. Dissolve this pre- 

 cipitate by adding 50 cubic centimeters of the sodium potassium 

 tartrate. Dilute to about 200 cubic centimeters, add solid sodium 

 bicarbonate and starch water, and titrate with standard iodin. 



Total Arsenious Oxid. Method III." Solutions Required. 

 Prepare the same solutions as were required for Method II. 



Determination. Boil 0.4 gram of the finely ground paris 

 green with 25 cubic centimeters of the sodium acetate solution 

 for from five to 10 minutes. Add concentrated hydrochloric 

 acid, a drop at a time, until solution is effected (about 10 cubic 

 centimeters of the acid is usually necessary). Add concen- 

 trated sodium carbonate solution, a drop at a time, until a slight 

 99 Haywood, Bureau of Chemistry, Bulletin 81, 1904 : 197. 

 Journal of the American Chemical Society, 1903, 25 : 963. 

 Bureau of Chemistry, Bulletin 107, 1907 : 26. 



