316 INSECTICIDES, FUNGICIDES, AND WEED KILLERS. 



gallons. To prepare this liquid dissolve the rosin and the carhonate of 

 soda in 6 gallons of water, boil until of a syrupy consistence, cool, 

 remove the excess of liquid, redissolve in the necessary amount of 

 water, add the ether and the essence of absynth, and when the mixture 

 is homogeneous add the ammoniate of copper. The preparation 

 should form a limped green liquid. This prepai^ation is termed 

 " Bordelaise insecticide". In 1902 more than 30 million stocks were 

 treated with this insecticide, either by steeping the grapes or by a very 

 fine jet. The amount consumed varies from 300-600 litres per 

 hectare (26-4-o2-8 gallons per acre). This preparation is recommended 

 for the destruction of parasites in creueral, for it kills all caterpillars. 

 Nobbe and Eichter found that ether could replace carbon disulphide 

 in the disinfection of the soil. They obtained by the disinfection of 

 the soil by an ether emulsion a yield of 4-5 per cent higher than that 

 of the untreated plot, and they attribute this favourable result partly 

 to the stimulating action of the small amounts of ether retained in the 

 soil. 



119. Mercaptan, C.Hj,SH. — Preparation. — By distilling sul- 

 phovinate of soda on the water-bath in presence of potassium hydro- 

 sulphide. 



Properties. — Mercaptan is a colourless liquid with a very un- 

 pleasant alliaceous odour, boiling at 30° C. (86" F.) and slightly soluble 

 in water. 



Use. — Mouillefert and Rommier tried mercaptan to exterminate 

 the phylloxera ; 10 drops of mercaptan in a 1-litre flask killed the 

 phylloxera in two days ; tried on the large scale, by distributing in six 

 holes dug round the infested stocks, a mixture of 12 '5 cubic centimetres 

 of mercaptan and 37"5 cubic centimetres of tar, the effect produced on 

 the phylloxera was almost nil. 



120. Formic Aldehyde, HCOH (Formol, Formaline).— Pre= 

 paration. — By the oxidation of methyl alcohol vapours at a high tem- 

 perature. It is manufactured commercially by the following process, 

 due to Trillat. Methyl alcohol is heated in a copper jacketed pan. 

 The vapours disengaged, mixed with air, are oxidized by passage over 

 fragments of coke heated to a dull red. The products are afterwards 

 rapidly abstracted by a vacuum at a more advanced stage of oxidation. 

 The commercial concentrated product contains 40-42 per cent of 

 formic aldehyde. In medicine or agriculture this solution is called 

 formol or formaline. Polymerized formol is also sold under the foi'm 

 of pastilles, which by heating disengage formol. 



Properties. — Formol possesses a strong sharp odour ; its vapour 

 irritates mucous membranes, the conjunctive in particular. Formol 

 is soluble in pure water up to 30 per cent, in presence of methyl alcohol 

 up to 42 per cent. It has extremely remarkable antiseptic properties, 

 much resembling those of corrosive sublimate. Like the latter it acts 

 on albumen and arrests, by its contact, the movements and growth 

 of micro-organisms. 



Action of Formol on Plants. — Loew *has pointed out its toxic 

 action on plants, but formol does not appear to have this action in the 

 doses in which it is used to combat plant diseases. Utilized almost; 



