SULPHURIC ACID (OIL OF VITRIOL). 



85 



porating the spores of rust and of caries with a drop of dilute sul- 

 phuric acid, which after being a certain time in the acid were sown or 

 examined by the microscope. In 1872 Kuhn examined the action of 

 sulphuric acid on the spores of the caries of wheat, and he found that 

 acid of the same strength is not capable of killing in the same time 

 the different spores of caries. A 5 per cent acid acted thus : — 



TABLE XII. — Shoiving the Action of Dilute Sul])huric Acid of 0-5 per cent 

 Strength on the Spores of Oats and '[Mieat. 



In -1892 Wuthrich examined the action of different acids, com- 

 pared with that of metallic salts, on the spores of — 



Ustilago Carbo, Tul. (smut of grain crops). — In a 0'49 per cent 

 sulphuric acid all spores are killed after fifteen hours' action at 

 20''-22° C. An acid of 0-049 gi-eatly prevents the formation of 

 zoospores, whilst acid of 0-049 per cent has no longer any injurious 

 action on the spores themselves. In 1895 Herzberg examined the 

 different rusts, and submitted their spores to the action of sulphuric 

 acid of various strengths. The spores of Ustilago Jensenii, Eost.,the 

 smut of barley, were found to be the most resistant. To kill these 

 spores they must be steeped fifteen hours in 3 per cent acid, whilst 

 those of the other Ustilagince are killed in much weaker acid. More- 

 over, the dilute acid has not the same action on the spores of the 

 same species but of different ages ; the mortal dose is given in the 

 following table : — 



TABLE XIII. — Showing the Strength per cent of Sulphuric Acid reqidred to 

 Kill the Spores of Smut of Barley, Oats, and Wheat of Different Ages. 



Puccinia graminis (black stem rust, summer wheat mildew) 

 Puccinia Bubigo-vera, D. C. (orange leaf rust, spring rust of corn) 



