MEECURIC CHLOEIDE (CORROSIVE SUBLIMATE). 293 



by spraying trunks and branches with a strong solution of corrosive 

 sublimate. 



Phylloxera vastatrix, Planch, (phylloxera of the vine). — Mouillefert 

 showed that it took four hours' contact in a 1 per cent solution to 

 kill this formidable aphis. The oldest insects succumb first, the 

 youngest last. By dipping the extremity of a root covered with adult 

 and young phylloxera into a solution of sublimate, the adults, the 

 sucking proboscis (rostulum) of which sunk in the root continually 

 pumps the juice, die in an hour, whilst the larvae persist. Used on 

 an infested vine the results were bad. Vines stripped to a depth of 

 15 centimetres (6 inches) were treated with 20 grammes of mercuric 

 chloride dissolved in 10 litres of water. After a few days the roots 

 examined still contained numerous living phylloxeras. Corrosive 

 sublimate is therefore powerless against this insect, for the physical 

 and chemical forces to which this salt is subjected in the soil soon 

 render it harmless. The same failure attended the attempt to poison 

 the sap by introducing into it 1 gramme of calomel (mercury proto- 

 chloride) in a hole, made at the base of the stock, which was closed 

 up forthwith (Ponsard's process, 1872). Neither had mercury bi- 

 sulphide (Catala's process) any action on this aphis. 



Schizoneura lanigera (woolly aphis). — The use of corrosive subli- 

 mate sprayings in concentrated solution does not destroy this aphis. 

 Thiel found per contra that an insecticide consisting of mercurial 

 ointment 1 lb., soft soap 7 lb., petroleum 2 lb., to which alcohol is 

 added at the moment of use, is one of the most active compositions 

 capable of killing all the aphides and of radically curing the apple- 

 trees. 



Ants. — Corrosive sublimate is used to poison the bait. 



Rodents. — To kill rats, balls are made from a paste of bread- 

 crumbs 12^ 07.., butter 6 oz., sublimate or nitrate of mercury 3 oz., 

 placed at the spot frequented by the rodents. 



log. Tin Crystals, SnCl,. — Preparation. — By dissolving tin in 

 concentrated hydrochloric acid, taking care there is an excess of tin. 

 The liquid heated until it marks 75° B. deposits on cooling the pro- 

 duct known as tin crystals. 



Properties. — Stannous chloride is very soluble in water. If the 

 solution be diluted it becomes cloudy, depositing an oxychloride, 

 SnCloSnO ; tin crystals are poisonous. 



Use. — Sbrozzi tried tin crystals as a substitute for blue vitriol 

 to overcome Peronospora viticola, De By. (mildew of the vine). He 

 found it was very inferior to blue vitriol and incapable of replacing it. 



