294 QUANTITATIVE AUHWt'LTUKAL ANALYSIS proper spray materials and mixing them so an to retain their insccticidal or fungicidal value is often a difficult and complicated problem.1 Chemical or physical changes may take place on mixing, resulting in compounds being formed which are injurioun to foliage, or in some eases the upray may become worthlw-w because the active killing agent has heroine inert. The various objectionable combinations are shown in Table XXVI on page 295. It will Ixs noted that Bordeaux mixture (copper sulphate and calcium hydroxide) with arsenal e of lead in permissible. It has been shown by analysis that when these arc* mixed the amount of soluble* arsenic is not mueh greater than when lead arson ate is treated with pure watei. On the other hand, lead arsenate and soap solution form an objectionable* combination because the load arsenale reacts with the sodium oleate of the soap, forming lead oleate (insoluble in water) nnd sodium arscnatc. The latter in soluble in water and the foliagf* in injured by the high concentration of soluble ar^enie. Lime-sulphur solution and lead arsenalc may !•«* safely mixed because analysis shows that the soluble arsenic is not tiitidt greater than when the arsenic compound in shaken with witter, The table shows tilao that Bordeaux mixture should not. In* mixed with the group of "emulsified oils" beeauw the emulsion of oils with water containing calcium hydroxide of Bordeaux mixture in not very satisfactory, the* result beinfc fhnf Mime cif the unemuisified oil remaining will injure the plant. The reverw- ble nature of soap and oil exnulKionn in general is diwunml by Bancroft2 as follows: "Since sodium oleate emulHificn nil in water nnd ealrium ulejite <«niul*i- fics water in oil, a mixture of the* two ^leufe* will Iwhiive differently, depending on the relative amounts. There will aln* he w?w* ratio of calcium to sodium at which the two oleates will praHindly !»iilnnci» other and the nlightest relative change will chungc flu* type of I lie emulsion." The reaction of calcium hydroxide of Bordeaux mixture with Bodium oleate of the soap will result in flu* formation of the? maximum quantity of calcium oleate* and thw will then 1 CM. Kxp. Kta. Circ., 195 (19IK), 2"Appli(i