SOME FLY POISONS FOR OUTDOOR AND HOSPITAL USE. 



32a 



The following are the substances placed in Classes I and II which have some 

 killing power : — 



Class I. 



Sodium arsenite (2% and 1%) kills flies effectively. 



Antimony arsemite is very insoluble ; a weak solution was fed to flies, and next 

 morning all were dead. As this chemical is a powerful human poison, no further 

 experiments were carried out with it. 



Sodium fluoride (5%, 2% and 1%) kills flies effectively ; at 5% and 2%, 80% 

 were killed. The 5% solution was a saturated one, as all the sodium fluoride would 

 not dissolve. This substance is not deterrent to flies, and its addition to sugar 

 solution does not make the latter distasteful to them. 



Sodium bifluoride (2% and 1%) is an effective fly poison, but is less soluble 

 than sodium fluoride and the 2% solution is a saturated one. 



Potassimn fluoride (2%) kills flies effectively, but is less soluble than the sodium 

 salt. 



Ammonium bifluoride (2% and 1%) kills flies effectively, but is less stable than 

 ammonium fluoride : at 5% strength, 80% flies were killed. 



Ammonium fluoride (2%, 1%, '5% and '2%) is a good fly poison : at 5% strengths 

 it is less effective, only 66% being killed. It is more soluble than the sodium and 

 potassium salts, but at high temperatures is said to be less stable, decomposing 

 and giving off hydrofluoric acid. However, as these poisons are primarily intended 

 for outdoor use, this instability, provided it did not occur at once on exposure, 

 would be of little account ; in fact, as all these fluorides are more or less poisonous, 

 though to a far less extent than the arsenic compounds, its property of decomposing 

 would be an added advantage, as it would obviate any danger from the substance 

 when lying about after use. Sodium arsenite, on the other hand, always remains 

 poisonous. The advantages of the ammonium and sodium fluorides as compared 

 with sodium arsenite are that, while being apparently as effective fly poisons, 

 they are far less poisonous to man. They are also cheap and readily obtainable. A 

 comparison between the kiUing powers of 2% and 1% strengths of sodium arsenite 

 and sodium and ammonium fluorides gave the following results : — 



Sodium and potassium iodates were tried by Miss Lodge and gave satisfactory 

 results, which we confirmed. In addition we tried anmionium iodate at 2%, 1% 

 (C357) b2 



