CHAPTEE II. 

 HYDROGEN SULPHIDE— SULPHUR. 



3. Hydrogen Sulphide (Sulphuretted Hydrogen, H._,S). — Pre- 

 paration. — By decomposing sulphides by a dilute acid. Iron sulphide 

 is generally used. It is dropped in pieces into a Wolff's flask, two-thirds 

 filled with water. By running in dilute sulphuric acid through a funnel 

 there are produced (1) iron sulphate and (2) sulphuretted hydrogen, 

 which is collected in a gasometer. 



Properties. ^Hydrogen sulphide is a colourless gas with the odour 

 and taste of rotten eggs. It burns with a blue flame. It is very 

 poisonous and treacherous, for it acts without any other warning than 

 a bad smell. A small bird perished in an atmosphere which contained 

 yJy^th ; a horse does not live long in an atmosphere containing -o^oth 

 of this gas. Under its influence the globules of blood are unable to 

 fix oxygen. 



Action on Plants. — Hydrogen sulphide is also injurious to plants ; 

 in its presence the leaves are coloured with yellow spots, which en- 

 tirely invade them, then the plants die. Schroder and Eems found 

 that to be the case in the neighbourhood of factories which disengage 

 a certain amount through their chimneys ; gasworks amongst others, 

 for coal gas always contains a certain quantity. An atmosphere 

 only containing y,^'g^th of hydi'ogen sulphide, that is to say, an amount 

 scarcely perceptible to the smell, but slightly blackening paper steeped 

 in lead acetate, is poisonous to the' plant. However, the toxic dose 

 varies greatly with the species of plants. Even roots themselves are 

 capable of absorbing it, and take a blue colour (Kny). 



Action on Insects. — -Mouillefert has examined the action of hydro- 

 gen sulphide on the phylloxera. On roots exposed in a flask filled 

 with this gas these parasites died in three minutes, but whilst at the 

 end of that time the adults were dead, the larvae and the eggs did not 

 appear to suffer. In an^atmosphere containing 1 volume of H^S in 

 150 volumes of air the phylloxeras were found dead after twenty- 

 four hours. If it contained 1 volume of H^S in 150 volumes of air 

 it took forty-eight hours to destroy these lice completely. Now, as a 

 litre of sulphuretted hydrogen weighs 1*5 gramme, an atmosphere con- 

 taining 1 per cent of this gas by volume only contains by weight 0*0015 

 per cent of that acid. As that amount represents the limit of toxicity 

 of this gas for the phylloxera, and as it requires 0'0016 gramme of car- 

 bon disulphide in 100 c.c. of air, it may be concluded that hydrogen 

 sulphide is as poisonous to insects as carbon disulphide. 

 (41) 



