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polysulphide rather than lower being formed in all cases. If the lime 

 is in excess, small quantities of free hydroxide may be present in the 

 dip, but the amount is limited b)'- the low solubility of the lime itself. 

 Calcium pentasulphide and calcium hydroxide can, however, co-exist 

 in the same solution eyen at the boiling point. 



3. The loogas- sulphur dip consists mainly of a mixture of carbonates, 

 polysulphides and thiosulphates of sodium and potassium, the amount 

 of polysulphide being very low and the amount of carbonate relatiyely 

 high. The reaction between alkaline carbonates and free sulphur is 

 yery imperfect eyen after prolonged boiling, and most of the sulphur 

 used in making the loogas dip is therefore wasted by passing into the 

 unused sediment. 



4. The kind of sulphur used in dip-making is of no consequence 

 pro\dded it is finely divided and fairly pure. Flowers of sulphur and 

 ground rock sulphur are equally suitable, but in the latter case a 

 guarantee of fineness of grinding should be demanded, 65° Chancel 

 being suggested as a reasonable specification. 



5. The quality of lime used is obviously of paramount importance 

 in making the lime-sulphur dip, but the lime generally available in the 

 Union of South Africa appears to be of very inferior grade. The saving 

 grace in cases where bad lime has been used in practice lies in the fact 

 that concentrations of polysulphide much below that obtained in a 

 well-made dip are still effective in curing scab. 



6. The lime-sulphur and caustic soda and sulphur dips are reliable 

 for the cure of scab. The loogas-sulphur dip also cured scab in the 

 experimental trial carried out, but its composition suggests that its 

 efficacy is largeh^ a matter of chance, and that it is therefore not to be 

 relied upon. 



7. The active constituent of the sulphur dips appears to be the poly- 

 sulphide, since thiosulphate, the only other important constituent, is 

 itself ineffective. Free base, if accidentally present, does not contribute 

 to the parasiticidal efficacy of the dips. A concentration of 0'6 per cent, 

 sulphur in polysulphide form is probably always high enough to effect 

 cure, while 0"3 per cent, showed itself as uncertain in action. The 

 polysulphide content of the home-made lime-sulphur dip is much 

 higher than that of the caustic soda and sulphur dip, but it is not advis- 

 able to dilute the home-made dip further than is already customary, 

 unless the lime used is known to be of very high quality. If com- 

 mercial lime-sulphur concentrates are used, dilution may be con- 

 veniently carried down to a concentration of about 0"8 per cent, 

 polysulphide sulphur. 



8. The sulphur dips i'f properly made (almost neutral to phenol- 

 phthalein) are harmless both to the sheep and to the wool. Solutions of 

 polysulphide, at the concentration used in dipping, have no action on 

 Avool even on prolonged steeping. On the fleeces of dipped sheep, 

 polysulphide is rapidly and almost quantitatively converted into 

 thiosulphate by atmospheric oxidation, and this occurs long before 

 the fleeces are dry. No depilatory substances are formed in detectable 

 amount, as intermediate products in normal decomposition. If, 

 however, free base be present in large quantity along with polysulphide, 

 it is possible for monosulphide to be formed as an intermediate product 

 in the course of atmospheric oxidation, and the possibility of depilatory 

 action then arises. Minor quantities of free hydroxide, up to about 



