SOAPS. 327 



places with a rag dipped in olive oil. Oil is currently used in Italy 

 against this aphis. Weiss advises to cut out the cankers and to treat 

 them with insecticides, and then to cover the wounds with oil paint, 

 which kills by asphyxia any aphis which might escape, and which 

 protects the wounds very efficiently. Henri advises to drench the 

 swellings on the trunk and the branches with a mixture prepared in 

 the following manner: Crush together alum 5 oz., sal ammoniac 5 oz., 

 and mix with sulphuric acid 3 oz., colza oil 100 oz. (all avoirdupois). 

 According to Kraft, it suffices to plug the wounds produced by the 

 woolly aphis with a mastic made by mixing plaster of paris and 

 linseed oil. Ouvray recommends as an excellent medium for destroy- 

 ing the woolly aphis, burning oil, in which 5 lb. of naphthalene has- 

 been incorporated per 10 gallons. At the fall of the leaf the diseased 

 apple-trees are brushed, the nodosities cut off," and coated with the 

 naphthalinated oil, taking care not to touch the buds. In March or 

 April the tree is again inspected, and if need be, the spots recently 

 invaded are plugged with the naphthalinated oil, applied by the brush. 



Coccides (cochineals). — Cochineals, kermes, etc., may be killed in 

 the same way as the woolly aphis, by oils and their emulsions with soap, 

 or with petroleum. It is only to be feared that the too large surfaces, 

 which it is often necessary to cover, may render the treatment injuri- 

 ous to the plant. This drawback disappears, according to Eeh, if the 

 oils are used as emulsions with soap or petroleum. Excellent results 

 are got, according to him, with an emulsion of soft soap 20 lb., vege- 

 table oil 15 lb., petroleum 10 lb., water 6 gallons. In America the 

 San Jose louse is overcome with whale oil and fish oil. 



Lepus cuniculus, L. (rabbit) ; Lep^is europcem, L. (hare). — Putrid 

 fish or animal oil protects crops and fruit trees. The bottom of the 

 tree may be coated, or the property surrounded by a fence consisting 

 of three cords dipped in this stinking oil, placed 8 inches from each 

 other. The commercial preparations known as " Lapintine," " Pomo- 

 line," " Picrofoetidine," consist of these oils. The leporides fear this 

 strong smell, much resembling the smell of its natural enemies, the 

 ferret, the martin, and the fox. 



124. Soaps are salts formed by the combination of a base with the 

 fatty acids present in oils and fats. All vegetable and animal oils and 

 fats yield soap with alkalies, and with metallic oxides generally. Their 

 physical properties depend chiefly on the base used. Soaps made 

 from alkaline metallic oxides are alone soluble in distilled water ; those 

 made from the oxides of other metals, lime or copper soap, for example, 

 are, on the contrary, insoluble in water. Amongst soaps made from 

 alkalies, hard soda soaps must be differentiated from soft potash soaps. 



Preparation.— 1. Hard Soaps. — They consist geneially of the 

 soda salts of margaric [palmitic], stearic, and oleic acids ; Marseilles soap 

 is the type of this sort. It is made by saponifying vegetable oils with 

 caustic soda. Glycerine is formed along with the soap, and is elimi- 

 nated in the mother liquor. In a large wrought-iron pan caustic soda 

 lye of 10° B. is heated, and the oil to be saponified run in gradually. 

 When the bulk is combined, the saponification is finished by adding lye 

 of 20° B. Boiling is continued until the whole is homogeneous. The 



