PYRKTHRl'M I'oWhKliS CONTAINING POISONOUS MKTALS. 13 



ANALYSES OF PYRETHRUM POWDERS. 



COI.LKCTION >! -\M1M.I 9. 



In order that -ample- of pyrethrum. repiv-rntat i\ e of all grades, 

 might be obtained. :i circular letter wa- forwarded to the chemist of 

 each of the experiment station-, with the request that they puivha-e 

 for us. upon the open market, three or four samples of those product- 

 sold under the name of either Pyrethrum. Huhach. Persian Insect 

 Powder, or I)almatian In-ect Powder. They were also asked to give 

 data, a- to the price per two-ounce -ample, the name and addiv-- of 

 the retail dealer, and the name and address of the pel-son who originally 

 prepared the sample. In answer to these letters In;. Cample- were 

 received, all of which were subjected to chemical examination. It is 

 helieved that these samples represent fairly well the present state of 

 the American market. 



Credit is due to the assistants in the laboratory. IVrnard II. Smith 

 and Harry AY. Houghton. who aided in performing the analytical work. 



MKTIlons AND IJKsn/rs OF ANALYSIS. 



Since lead, potassium, and harium chromate have all a bright yellow 

 color, and any of them might he used to color the pyrethrum powders, 

 tests for all of these substances were made in the samples under exam- 

 ination according to the following methods: 



(hnil'tinl'it; f.str'ur I,<n7. Ash about '2 grams of the sample in por- 

 celain and treat with a little water and tihout 20 cc of concent rated 

 hydrochloric acid in a porcelain dish. Place on the steam bath and 

 -team for about one-half an hour or until all the lead is in solution and 

 the chromium reduced and in solution. Filter after dilution. Add 

 sodium carbonate until the solution is alkaline and then add acetic 

 acid until the solution is just acid. Filter and add a solution of potas- 

 sium chromate. A yellow precipitate or cloudiness indicates lead. 



(Juiilttntji'i- f.xt f<,,' Inii-'mni. "Ash about '2 o-rams of the sample in 

 porcelain and treat with hydrochloric acid as directed for lead. Fvap- 

 orate to dry ness and take up with about 0.8 cc of hydrochloric acid. 

 Filter and pass hydrogen sulphid through the tiltrate. Filter otl any 

 sulphids that may precipitate and test for barium in the tiltrate with a 

 tew drops of dilute sulphuric acid. 



^^///'A////v 1,-xt fui> <-/u'<nntiiiii. Ash about '1 grams of the -ample in 

 porcelain. Treat this with about four times it- weight of a mixture 

 of equal parts of sodium carbonate and potassium nitrate, and fu-c. 

 Dissolve in water on the steam bath and filter. M ike slightly acid 

 with acetic acid and test with lead acetate for the presence of chromium. 



Testing the powders by the above methods showed that whenever 

 chromium was present lead was also present, these two evidently being 

 combined as lead eliminate. A quantitative estimation was al-o made 

 of the chromium present according to the following method of analysis 

 and the chromium was calculated to lead chromate. 



