SULPHURIC ACID (OIL OF VITRIOL). 83 



Natural Occurrence. — H^.SO^ is widely distributed in nature as 

 sulphates of lime, CaSO^, of baryta, BaSO^, of soda, Na^SO^, and of 

 potash, K^SO^, etc. It is found in the free state in some springs in the 

 neighbourhood of volcanoes. 



Properties. — The commercial acid of 66° B. (168° Tw.) is a 

 colourless, odorous, viscous, oily liquid of sp. gr. 1"84. "When water is 

 mixed with the acid so much heat is developed that it may become 

 dangerous if the water is added to the acid. Care must therefore be 

 taken in diluting the acid with water to run the acid gently into the 

 right amount of water with constant stirring. H^S04 ^^^ a great 

 affinity for water, and lapidly carbonizes organic matter. 



Action of Sulphuric Acid on Plants. — This acid exerts a cor- 

 rosive action on the organs of the plants touched by it. A very small 

 dose of this acid (even dilute) destroys the chlorophyll and degener- 

 ates the cell-walls, thus giving rise to a profound disturbance in the 

 life of the plant. 



Transpiration is less abundant, and that of itself diminishes or even 

 abolishes completely the production of synthetic organic matter, the 

 leaves brown, wither, fall, and the growth of the plant is visibly ar- 

 rested. If the action of this acid on a plant be prolonged it soon dies, 

 for the acid penetrates rapidly into the interior of the trunk, and the 

 circulation of the sap is stopped. The same result occurs when a 

 plant is in contact not only with the dilute acid but also with sub- 

 limed sulphur which contains HoSO^, and under the influence of 

 sunlight is converted into H^SO^ ui the leaf itself. 



Action of Sulphuric Acid on Fungi. — Plants not containing 

 chlorophyll suffer much less than green plants in contact with HoSO^. 

 However, owing to its hygroscopic nature, H^.SO^ diluted to 0-5 per 

 cent exerts a corrosive action on fungi. Laboratory trials made by- 

 dipping the spores into a drop of H.^SO^ diluted to 0*5 per cent show 

 that such dilute acid destroys in most instances the vitality of the 

 spores, provided that its action be sufficiently prolonged. In practice 

 the 0*5 per cent acid is quite inadequate to destroy the spores and 

 mycelium of fungi, and stronger, sometimes even the 168° Tw. acid 

 must be used. It will be easily seen that at that degree of concentra- 

 tion HoSO^ cannot be put in contact with the leaves of plants, and 

 that it should be limited to applications on the trunk, or to disinfect 

 certain seeds ; in a wood it can only be used when there is no active- 

 plant growth. Under such conditions, plants do not appear to suffer 

 from the sulphuric acid treatment. When H2SO4 is used in combina- 

 tion with anti-cryptogam ic metallic salts, its corrosive properties be- 

 come valuable, because in attacking the protective membrane of the 

 parasites it enables the poison to reach and destroy them more readily. 

 In combination with green vitriol in the winter treatment of anthrac- 

 nose of the vine, sulphuric acid is in current use, and of great service. 



Use against Parasitic Fungi. — Sulphuric acid has been recom- 

 mended for some years to wash seeds to free them from the spores of 

 different fungi which might be brought on to cultivated land. Noel 

 found in 1866 that steeping in the 0*5 per cent acid sufficed to free 

 seed-corn from anthracogenous parasites. He stirred up a hectolitre 



