LEAD ARSENATE 



Lead arsenate is the standard arsenical 

 poison for chewing insects. It is made by 

 mixing equivalent amounts of solutions of 

 either lead acetate or lead nitrate with sodium 

 arsenate. 



Calculation. — Inquire as to the character 

 of the sodium arsenate available — as to its 

 condition of hydration and degree of purity 

 — and from the equation, 



Na^HAs04 • 7H2O + Pb(N03)2 = PbHAs04 

 + 2NaN03 + 7H2O, 



calculate the amount of disodium hydrogen 

 arsenate that will be necessary to react with 

 20 grams of lead nitrate. 



If the salt is hydrous the 7H2O will be weighd out 

 and must be calculated; if anhydrous the 7H2O must 

 be left out of the calculation. If the salt is 80 per cent 

 pure the amount to be used must be increased by divid- 

 ing by 0.80. 



Dissolv the lead nitrate in 50 cc. of warm 

 water and dilute to a total volum of 350 cc. 

 with cold water. Similarly dissolv the req- 

 uisit amount of arsenate of soda in a little 

 warm water and dilute to 350 cc. with cold 



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