116 Dr. Dana oil the Manufacture of Sulphuric Acid, 



which is occasionally found in the lead-houses in this country; 

 but the analysis which I made of the substance to which the 

 following remarks refer, showed its composition to be similar 

 to that stated by Dr. Henry. My experiments were directed 

 chiefly to the effects of the formation of this crystalline sub- 

 stance in the lead-houses. Such as they are, I submit them 

 to your disposal. Very truly yours, 



London, June 12, 1833. SAMUEL L. Dana. 



The solid is confusedly crystallized in needles, or aggregated 

 in crystalline grains, which appear like those produced in 

 some sublimations. I have observed it also in flat four-sided 

 prisms lj inch long, and in interlacing filaments from 3 to 

 5 inches in length. 



1. Dissolved in a small portion of water, violent efferves- 

 cence occurs, and red fumes appear as gas escapes from the 

 water. The same phenomena occur if dissolved in a large 

 quantity of water, except that the red fumes are less abun- 

 dant : the water becomes deep blue, which changes to green, 

 and finally the water becomes yellowish. If the solution of 

 the crystalline matter is largely diluted with water, the colour 

 disappears, but always at the point of solution; at the point of 

 contact, between the solid and the water, there the colour is 

 blue, at the moment of escape of gas from the solid. The 

 green-coloured solution effervesces strongly on further dilu- 

 tion with water, giving off deutoxide of azote, and becomes 

 blue green. 



2. All the above phaenomena appear if the experiment is 

 made in an atmosphere of hydrogen, nitrogen, or carbonic 

 acid gas, but the red fumes are less abundant. 



3. If the crystalline solid is laid on snow, it tinges it imme- 

 diately deep blue. There is no escape of gas. It melts the 

 snow and sinks into it like hot iron, the temperature falling at 

 the same time. From +30° to —16° is the greatest reduc- 

 tion which I have observed; at —16° the solid appears not 

 to be acted upon, and the blue tinge gradually disappears. 



4. The solution in water was found to be sulphuric acid, 

 nitrous acid, and deutoxide of azote. 



5. The solid dissolves very slowly in oil of vitriol of sp. gr. 

 1*81< ; a few bubbles of air escape. The solution contains ni- 

 trous acid, which cannot be driven off by boiling. 



6. It dissolves with effervescence, greater or less, according 

 to the density of the oil of vitriol. Effervescence is brisk when 

 the sp.gr. of theoil of vitriol is from 1*35 to 1 *45. In oil of vitriol 

 ofsp.gr. from 1-60 to 1*70 it is difficultly soluble, and there is 



