370 INSECTICIDES, FUNGICIDES, AND WEED KILLERS. 



bonic acid of the air into carbonate of soda and naphthol which is 

 very adherent to the leaves and resists heavy rain. 



Gloeosporium niacropus, Sacc. (orchid mildew). — Man^dn advises use 

 of 2 per cent naphthol ; it prevents the germination of the spores. 



Poppy {(Eillei] Disease. — Mangin recommends to steep before trans- 

 planting the end of the slips in a solution of 15 lb. of naphthol and 45 

 lb. of soap in 100 gallons of water or 5 oz. of naphtholate of soda in 

 62tV gallons of water (5 grammes in 10 litres). 



Fusarium roseum. — Mangin advises the disinfection of the soil by a 

 solution of naphthol 1-2400. This method is disputed by Delacroix. 

 Sacardo advises with the same object a solution of 0'5 per cent of 

 naphtholate of soda against rust of poppies [CEillet], rose-bushes, 

 asparagus, etc. 



142. Methyl Violet or Pyoctanine. — Pyoctanine is a methylated 

 or ethylated rosaniline obtained either by heating rosanilines to about 

 140° C. with methyl or ethyl chlorides or iodides dissolved in alcohol, 

 or by treating dimethylaniline by carbon oxichloride in presence 

 of aluminium chloride (yellow pyoctanine is a hexamethylated 

 auramine). 



Properties. — Methylated and ethylated rosanilines in the form of 

 salts constitute crystallized violet colouring principles soluble in 

 water. They are used to make aniline inks, and in the dyeing of fabrics. 

 Pfeffer determined the injurious action of pyoctanines on phanerogams. 

 Kreminski, and especially Stilling and Wortmann, have examined the 

 antiseptic action of pyoctanines. They have shown that it suffices to 

 sterilize a medium, such as meat juice, for it to contain 0-005 per cent of 

 methyl violet, or 0'5 per cent of yellow pyoctanine. The Staph nlococcus 

 pyrogenus aureus does not develop in a solution of 1 in 2,000,000 of 

 methyl violet. The Penicilliiim glaucum does not develop in a medium 

 drenched with a solution of 1 in 10,000 of pyoctanine violet. The 

 pyoctanines do not coagulate albumens, like powerful antiseptics such 

 as corrosive sublimate, formol, etc., but alhumenized bodies have a 

 certain affinity for these products and eliminate them from water whilst 

 becoming dyed. The colour concentrates itself there, and if the amount 

 absorbed is sufficient the corpuscles are arrested in their evolution, the 

 dyed bacteria give up their colour to pure water, and they can become 

 completely decolorized and regain by this fact their primitive vitality 

 if the surrounding water is in sufficient quantity to extract the colour 

 simply dissolved in their plasma. 



Use. — Acrostalagmus albus. — Stilling found that it sufficed to water 

 the infected dung or the dunged borders with a dilute solution of methyl 

 violet to stop the development of this fungus. 



