1'YRKTllRl.M I'oWDKRS CONTAINING POISONOUS ICETALS, 17 



<t,f, i iiit'nttii/ <-/u'<nn!r,n-i<l. Wei^h out from '2 to -1 



of the sample. A-h in a porcelain dish and allowto cool. Treat with 



a little water and a larnv amount of concentrated hydrochloric acid and 

 evaporate t<> dr\ lie--. Treat ULi'ain with concentrated hydrochloric 

 acid and evaporate (,, dryne-^. 



Take up the re-idue with ahout <>.> << of concentrated hydrochloric 

 acid with the aid of heat. Filter and pass hydrogen >ulphid through 

 the solution until all lead i> precipitated. Filter and evaporate the 

 tiltrate to dryne--. Take up the re-idue with a little water and 1 cc 

 of hydrochloric acid with the aid of heat. Precipitate out the 

 chromium (with iron, aluminum, and some phosphoric acid) by means 

 of ammonia, taking care not to add any excess of ammonia. Filter 

 and wash with hot water. Dissolve the precipitate on the tiller by 

 means of hot dilute hydrochloric acid and evaporate to dryno-. Take 

 up with a little hot water and ' to s drop- of concentrated hydro- 

 chloric acid, heating for a short time if necessary. Transfer to a 50 

 cc 01- Inn (( Hash and make up to the mark. Now prepare an alkaline 

 permanganate solution in the following manner: Make an approxi- 

 mately X 1<> solution of potassium permanganate and standardize it 

 against ammonium ferrous sulphate. Measure out exactly a liter of 

 this solution and add a few grams of sodium carbonate and 1 gram of 

 sodium hydroxid and make the entire volume up to 2 liters. This is 

 the standard solution required. 



A convenient number of cubic centimeters of this standard is 

 measured into a beaker and about 50 cc of distilled water, accompanied 

 by a little sodium carbonate, is added. The solution of chromium 

 previously prepared is then run in from a burette, while the contents 

 of the beaker are boiling, until the pink color is dissipated and a pure 

 yellow color results. Knowing the strength of the permanganate and 

 the number of cubic centimeters of the chromium solution used, one 

 can calculate the percentage of chromium in the original powder accord- 

 ing to the following equation: 



CrCl 3 + KMn0 4 + 4 KOH = K 2 CrO 4 -h MnO 2 + 3 KC1 + 2H 2 O 



In Table II are found the results obtained upon the samples of 

 pyrethrum powder examined: 



TABLE II. 



nf />;/i-<th/-n,i/ powders for coloring mutter." 



26958 No. 7& 03- 



