44 INSECTICIDES AND FUNGICIDES. 



It will at once be seen from Table VII that nearly all of these 

 mixtures are made up principally of one or more of the following 

 substances: Borax, pyrethrum, cloves, and sassafras. The first two of 

 these have been used for years in driving away vermin from the places 

 they frequent. The second two, although not so often used, are doubt- 

 less efficacious, since it is commonly supposed that roaches, etc., are 

 driven away by high-smelling oils and spices. 



The analyses, as given in the table, in most cases explain themselves, 

 so it is unnecessary to go into further detail. Two samples, however, 

 are worthy of further note, namely, 20504 and 23493. The first of 

 these appears to be a by-product or an unpurified product in the 

 manufacture of ultramarine (hence the sulphur, sodium, carbonate, 

 and ultramarine), along with small amounts of borax and pyrethrum. 

 Three of these, sulphur, borax, and pyrethrum, amounting on the 

 whole to not more than one-third of the mixture, give to it its only 

 value as an insecticide. Sample 23493, besides containing borax and 

 sassafras root, also contains about 39 per cent gypsum, which adds 

 weight, and is valueless as a vermin exterminator. Very fine pow- 

 ders, such as powdered gypsum, are said by some to drive awa}^ ants, 

 since they seem to dislike to crawl through finely divided substances. 



ROACH PASTES. 



According to formulas published in chemical receipt books and phar- 

 maceutical journals, these pastes all have free phosphorus as their 

 active poisonous constituent. This is sometimes mixed with molasses 

 and flour or corn meal, sometimes with glucose sirup and flour or 

 corn meal, and sometimes with sugar, lard, and flour or corn meal. 

 These preparations are very efficacious in ridding the house of cock- 

 roaches and rats, since they eat the paste and are killed outright instead 

 of being driven away to some other place. Great care should be taken 

 in the use of such preparations, since when taken internally they are 

 poisonous to human beings and household animals. 



METHODS OF ANALYSIS AND DISCUSSION. 



The methods of analysis used for this class of compounds are as 

 follows: 



Phosphorus. a Extract the phosphorus from a weighed quantity of 

 the paste by repeatedly rubbing the sample up with small quantities of 

 carbon bisulphid. Filter each time, keeping the filter covered to pre- 

 vent oxidation. After all phosphorus is extracted treat the filtrate 

 with a 5 per cent solution of silver nitrate, which will precipitate the 

 phosphorus as silver phosphid. Oxidize the precipitated phosphid by 

 treating with 30 to 40 cc of dilute nitric acid and shaking well. 

 Finally, heat gently to oxidize the remaining phosphid and drive off 



aChem. Zeit., 1893, XVII, 1244, 1245. 



