AESENIURETTED HYDROGEN. 93 



gnawing orchid roots. Paste pills made from honey and phosphorus 

 and laid on the pot of the plant attacked rapidly destroy the insect. 



Gryllotalpa vulgaris (mole-cricket).— Elias Hugo destroys it by 

 laying poisoned pastes of maize, starch, water, and phosphorus in the 

 burrows and stopping up the orifices. The mole-crickets disappear in 

 twenty-four hours. 



Formica (ants). — To poison ants Debray introduces phosphorus 

 paste made from molasses and phosphorus. The orifices of the nest 

 are then stopped. 



12. Phosphoretted Hydrogen, PH3. — Preparation. — (1) By the 

 action of phosphorus on caustic alkalies or the hydroxides of the 

 alkaline earths in presence of water and under the influence of heat. 

 (2) By decomposition of calcium phosphide by water alone or by 

 hydrochloric acid. 



Properties. — Phosphoretted hydrogen is a colourless gas with a 

 strong garlic smell, inflaming at 60° C. (140° F.). It is poisonous, 

 and acts especially by depriving the haemoglobin of the blood of the 

 oxygen fixed thei-ein. 



Use. — Phosphoretted hydrogen is recommended for combating the 

 phylloxera. Mouillefert showed this gas to be five times more poison- 

 ous than prussic acid. An atmosphere containing 0*5 per cent of 

 phosphoretted hydrogen is very injurious to the phylloxeras, but the 

 latter are not destroyed until after they have been fourteen hours in 

 an atmosphere containing 1 per cent of this gas. Experiments on 

 the large scale have given variable results ; those of Mouillefert, a 

 negative one ; those of Rosier, a perfect one. The former wrought 

 thus : 20 grammes (310 grains) of phosphide were laid in three holes 

 of 50-60 centimetres (20-24 inches) in depth, at equal distances round 

 a stock, and then closed. The moisture and carbonic acid in the soil 

 decomposed the calcium phosphide. Rosier, on the other hand, re- 

 commends the digging of holes around the stock, and to lay therein 

 several layers of quicklime, on which a small piece of phosphorus is 

 placed. The holes, filled up, are covered with water and then stopped 

 with clay. Rosier recommends this treatment as efiicacious, and 

 without any injurious effect on the vine treated ; it is done in the spring, 

 Mouillefert ascribes the bad result of his experiments to the rapid 

 oxidation which goes on in the soil, and to the feeble diffusion of 

 phosphoretted hydrogen, which is less rapid than carbon disulphide. 



13. Arseniuretted Hydrogen, ASH3. — Preparation. — By decom- 

 posing certain arsenides, such as those of zinc and tin by dilute sul- 

 phuric acid. Zinc arsenide is obtained by fusing 100 parts of zinc 

 with 75 parts of arsenic in an earthenware retort. 



As._,Zn3 + 3H.,S0^ = 2ASH3 -f ^ZnSO^. 



Properties. — Arseniuretted hydrogen is a colourless, inflammable 

 gas with a strong garlic odour. It is exceedingly poisonous and must 

 not be breathed even when it is diluted with much air. 



Use. — In America it has been tried to destroy the kermes of fruit 

 trees. Coquillet covered the trees with a tent, under which he caused 

 AsHg to be disengaged, but the results were not so satisfactory as 



