271 



Their conclusions confirm those of the above American workers on many 

 points, and throw new light on others. In any case the American 

 investigators used pure or quasi-pure products, especially limes contain- 

 ing only traces of impurities, whereas the authors used commercial 

 limes that were partly carbonated, as is generally the case. The 

 resulting differences are very important. 



Lime-sulphur solutions may contain the following substances : — 

 In solution : Calcium thiosulphate, calcium tetrasulphide, calcium 

 pentasulphide, and calcium oxysulphide ; in sediment : sulphur, 

 lime, calcium sulphite, calcium sulphate, and calcium oxysulphide. 

 All the other substances that have been reported, such as lime in 

 solution, hydrosulphates, etc., are not met with. 



The relative proportions of the dissolved constituents vary according 

 to a number of factors. At ordinary temperatures, and after several 

 months, oxysulphides of calcium, calcium thiosulphate, and a little 

 calcium tetrasulphide are formed. The quantity of soluble salt 

 formed increases with a rise of temperature up to 100°C. (212°F.), 

 and at high temperatures the sulphides predominate. This results 

 in an actual increase of thiosulphate, though its percentage to the 

 sulphides decreases. The content of dissolved sulphur increases with 

 the period of boiling up to 45 minutes, after which it decreases. At 

 first, a tetrasulphide is formed ; the pentasulphide appears gradually 

 afterwards. 



The maximum quantity of sulphur in solution is obtained when 32 

 parts of sulphur to 1 part of lime are used. Any variation of this 

 proportion decreases the amount of sulphur. Above 29 of sulphur to 

 1 of lime, pentasulphides are obtained ; below that proportion a mixture 

 of tetrasulphide and pentasulphide results. The percentages of lime 

 and of sulphur that dissolve increase as the quantity of water is 

 increased up to 3- 1 parts water to 1 of the mixture of lime and sulphur. 

 If more water is used the percentages diminish. The proportion of 

 calcium thiosulphate decreases with an increase of the time of cooling. 

 The greater the surface exposed to the air the more calcium thio- 

 sulphate is formed. Magnesium causes considerable loss of sulphur 

 and leads to a release of sulphuretted hydrogen. Limes containing 

 magnesium should therefore be rejected. If the sediment contains 

 an excess of lime, calcium oxysulphides are formed. 



It will be seen that in agricultural practice it is very difficult to 

 master all the above factors and to obtain a standard solution of 

 constant strength unless the services of an expert chemist are available. 

 The density of the solution is no guide to its sulphur content. Further- 

 more, sprayers with copper parts soon perish ; either aluminium or 

 some special brass alloys must be used. The variability of its 

 action and its destructive effect on the usual sprayers have retarded the 

 general adoption of lime-sulphur, in spite of its manifest advantages. 

 Nothing can replace it in certain cases, and this spray is very much 

 cheaper than the copper solutions and insecticides in common use. 



TITLY.A.RD (R. T.). Report on the Neuropteroid Insects of the 

 Hot Springs Region, N.Z., in relation to the Problem of Trout 



Food.— P;'oc. Linn. Sue. N..S.W., Sydnev, xlv, pt. 2, 16th August 

 1920, pp. 205-213, 2 figs ; also' N.Z. J I. Set. S- Tcchnol, 

 Wellington, iii, no. 5-6, January 1921, pp. 271-279, 2 figs. 



The food of trout consists largely of insects, especially of Pyronoia 

 /estiva (green manuka beetle) and caddis flies and other Neuropteroid 



