PREPAEATION OF SULPHUR. 43 



in which flowers of sulphur are first collected before the chamber 

 becomes heated. The sulphur which follows comes in contact with 

 the more hot sides, and when these have reached a temperature of 

 110° C. (236" F.) it condenses in the liquid slate and runs into wooden 

 moulds through an opening for the purpose. Brimstone is so ob- 

 tained. For agricultural purposes sulphur is prepared under different 

 forms : (1) Sublimed suljyhur, or Floioers of sulphur, is an extremely 

 fine powder of a yellow straw colour, which, examined under the 

 microscope, appears as small rounded grains, studded with small 

 points. It often contains sulphurous acid and sulphuric acid in the 

 proportion of 1 per cent. -(2) Ground stilpliur is obtained by the 

 pulverization, grinding, and sifting of brimstone. Ground sulphur 

 can now be obtained, the fineness of which almost equals flowers of 

 sulphur. It has the advantage of being neutral and cheaper. It con- 

 sists of angular grains, and is paler than sublimed sulphur. (3) Wind- 

 hloicn sulphur is of a bright colour, absolutely neutral, and can be 

 passed through a 100 sieve, which proves that it is almost as fine as pre- 

 cipitated sulphur. It shows branching particles under the microscope 

 and grains of regular dimensions. Like ground sulphur, it neither 

 contains sulphurous nor sulphuric acid. It is dearer than ground 

 sulphur. (4) Precipitated sul])hur is impalpable. It is extracted 

 from the spent material used for gas purification ; when it is imperfectly 

 purified it still contains tar, cyanides, and, as it is somewhat hygro- 

 metric, it burns the leaves. Hence its restricted use in the sulphuring 

 of plants. It is obtained, also, by a chemical method : alkaline poly- 

 sulphides, treated by hydrochloric acid in aqueous solution, give ofl" 

 hydrogen sulphide, aud deposit at the same time a precipitate of almost 

 white sulphur. This precipitated sulphur is dearer than the foregoing ; 

 it contains sulphuretted hydrogen and alkaline sulphides. (5) Mix- 

 tures containing sulphur. — In nature sulphur often occurs mixed with 

 gypsum, carbonate of lime, sand, in proportions varying from 5 to 40 

 per cent. Such minerals are ground finely and marketed as Apt sul- 

 phur and Briabaux sulphur. The " Minerale Greggio " extracted in 

 Sicily is an earth containing 40 per cent of sulphur, 2 per cent of 

 alkaline carbonate, 11 '8 per cent of carbonate of lime, 42 per cent of 

 magnesia, 36 per cent of sulphate of lime, a little iron, clay, and 

 arsenic. The value of these mixtures depend on their sulphur con- 

 tent; the gypsum and car b mate of lime have no anticryptogamic 

 property. In many cases they are preferred, and that is what has 

 contributed to the preparation of artificial mixtures containing 10- 

 50 pei' cent of sulphur only. The Fonta powder, used since 1857, 

 contains 10 per cent of sulphur and 90 per cent of talc. A marble 

 worker of Saint-Beat, having tried a mixture of 50 per cent of ground 

 marble, and 50 per cent of sulphur, found that this very efficient 

 treatment occasioned no scorching on the vine, even during great heat. 

 Neutral mixtures have, therefore, been prepared for this purpose, con- 

 taining 50 per cent of sulphur and 50 per cent of gypsum, carbonate 

 of lime, oi- clay. Now that cryptogamic diseases, like mildew and 

 black rot, have invaded the vine already attacked by oidium, attempts 

 have been made to reduce the multiphcity of treatments by mixing 



