VEEDIGRIS COPPER ACETATE. 281 



portional to the molecular weight of the copper compound contained 

 in a given amount of liquid, and the rapidity of the action is propor- 

 tional to the degree of solubility of the copper compound. The weak 

 acid or alkaline reaction of these preparations has no secondaiy 

 curative effect. Verdigris bouillie must, therefore, be prepared with 

 a weaker dose of verdigiis than that of the blue vitriol, which enters 

 into the composition of bouillie bordelaise, firstly because blue vitriol 

 only contains 25 per cent of metallic copper, whilst verdigris contains 

 35 per cent ; secondly because verdigris is partially soluble in water. 

 The dose of 1'5 per cent is not exceeded in bouillies, it is mostly 

 lower than this and descends to O'l per cent. Verdigris bouillie has 

 the same drawback as blue vitriol and eau celeste. It leaves no 

 visible mark on the plants, and renders the control of the work of the 

 operator difficult. To obviate this drawback, Chuard and Porghet 

 add potter's clay, china clay, carbonate of magnesia, gypsum, or chalk. 

 It is, moreover, comparatively dearer than other copper preparations 

 of equal copper content, which is an obstacle to its becoming popular. 



Use. — Verdigris has been used as an anticryptogamic in France 

 since 1890, and in America since 1892. 



Peronospora viticoia, De By. (mildew of the grape). — In virtue of 

 the energy and adherence of verdigris, three treatments suffice (Bencker). 

 The first fifteen days to three weeks after the issue of the first leaves 

 with a 1-5 per cent bouillie, 2 hectolitres per hectare (17-6 gallons per 

 acre) suffice. If the invasion of mildew be very great, supplementary 

 treatments with 0"35 per cent of verdigris are required. Cuboni ad- 

 vocates this treatment. 



Guignardia Bidivelli, V. and E. (black rot of grapes). — Galloway 

 with six sprayings with 0-1 per cent verdigris bouiUie obtained 90-47 

 per cent of sound grapes against 19-06 per cent on untreated vines. 

 According to experiments by Eathay and Havelka, the spores of 

 Guignardia are killed after twenty minutes by steeping in 05 per cent 

 bouillie. Linhart got the same results with copper acetate. Eougier 

 recommends Viala and Pacottet's bouillie consisting of neutral copper 

 acetate 1 lb., acetic acid 8 fluid oz., water 10 gallons. 



Puccinia (rust). — Galloway got interesting results by spraying a 

 field of grain four times, on 6, 16, and 25 June, and 5 July ; with a 

 0'3 per cent bouillie he entirely prevented rust. The uredospores of 

 Puccinia coronata were prevented from germinating by 1*0 per cent 

 bouillie (Hitchcock and Carleton). 



Entomosporium maculatum, Lev. (leaf scald of the pear-tree). — 

 Halsted found that 0-2 per cent bouillie suffices to overcome this 

 parasite, and Fairchild advocates verdigris as the best preparation 

 against spots of the leaves of the pear-tree. 



PJiytophthora infestans, De By. (potato disease). — Whilst Pearson 

 found verdigris as energetic as bouillie bordelaise, Sturgis found it 

 without action on Phytopihtliora PhaseoU (Lima bean mildew). 



Rot of Grapes. — Consecutive attacks of Cochylis. These are pre- 

 vented, according to Vermorel, if the grapes are sprayed with verdigris. 



I02. Copper Acetate, CujCoHyO.J-H.p.— Preparation. — Neutral 

 copper acetate, or crystallized verdigris, is obtained : (1) By treating 



