hydrochloric acid a drop at a time until solution of the green is effected (about 

 10 cc of the acid will be necessary). Add concentrated sodium carbonate solu- 

 tion a drop at a time until a slight precipitate appears, then add 50 cc of a J to 

 t; per cent sodium potassium tartrate solution, and finally sodium bicarbonate 

 in excess. Titrate with standard iodin solution in the usual manner. 



SonirM-ArKTATK-soi.rm.i-: AKSKNIOTS o.xin (PROVISIONAL). 



Snl.lTlONS KKOJ'IKKD. 



A solution of sodium acetate containing IL'.-"> grams of the crystallized salt in 

 each 25 cc ; a solution of starch; and a twentieth-normal solution of iodin pre- 

 pared as indicated above. 



METHOD, 



Digest 1 gram of paris green over the flame for about " minutes, with 25 cc of 

 the .-odium acetate solution described above, cool the solution, make up to 100 

 CC, lilter off 50 cc through a dry filter, and titrate with twentieth-normal iodin 

 solution. 



WATER-SOLUBLE ARSENIOUS OXID (PROVISIONAL). 



SOLUTIONS REQUIRED. 



A -larch solution and a twentieth-normal iodin solution, prepared as described 

 ibove, 



MKTHOD. 



One gram of paris green is treated with 1,000 cc of water (previously boiled 

 to e\pel carl)on dioxid, and again cooled to room temperature) in a large flask. 

 The Mask is stoppered and shaken eight times each day for 10 days. At tin- 

 end of this time the solution is filtered off through a dry lilter. Two hundred 

 cubic centimeters of this filtrate are treated with sodium bicarbonate and titrated 

 with t \\eiitieth-normal iodin solution. 



TOTAL COITKK <>xn>, MKTHOD I (OFFICIAL). 

 METHOD. 



The cuprous o\id obtained in Method I for total arsenious oxid, by boiling 

 th- paris green with sodium hydroxid, is poured on the filter and well washed 

 \\ith hot \\ ater. after an aliquot portion of the filtrate has been taken for the 

 determination of arsenious oxid. It is then dissolved in hot dilute nitric acid 

 and made up to a volume of 250 cc. Fifty to 100 cc of this solution is used for 

 the electrolytic determination of copper, as described on page 7, paragraph 2-b 

 of Bulletin It. i revised), Bureau of Chemistry, U. S. Department of Agriculture. 



TOTAL COPPER OXID, METHOD II (PROVISIONAL). > 



SOLUTIONS REQUIRED. 



A standard twentieth-normal solution of sodium thiosulphate is prepared by 

 Sving 21. s giams of the cr\ st alli/ed salt in 2 liters of water. This solution 

 is -laiidardi/ed again.-t ('. P. copper foil dissolved in nitric acid by the method 

 of analysis given in the following paragraph. 



METHOD. 



An aliquot portion of the nitric acid solution of copper oxid, used in Method I 



for total copper oxid, i- made alkaline with sodium carbonate, then made 



/// acid \\ith acetic acid, diluted with water, and a considerable quantity 



1 Has been r-ruimiieini-.i i.y :i n-feree as an "optional orticial method. 



