444 [AsSEMBI^Y 



a combination of persulpliate of iron, and ferrocyanuret of potas- 

 sium. The ferrocyanuret of potassium is made by burning car- 

 bonate of potassa with hoofs, dried blood, or horns, in an iron 

 vessel; which form cyanuret of iron. The soluble portions are 

 then taken out with water, and sulphate of iron added, until the 

 Prussian blue will no longer be decomposed by the potassa. 

 The ferrocyanuret of potassium is then set to crystalize, when 

 truncated octohedral yellow crystals are obtained, called prussiate 

 of potash. There is a process of dyeing a magnificent blue with 

 this material, that does not suffer by exposure to atmospheric air 

 in all its vicissitudes, acids even do not injure it ; and boiling 

 in alum-water has no eflect upon it. 



Our importations of indigo are large. On the first of January 

 we had a stock of India, numbering 30,332 chests. We have 

 received, during twelve months, 7,838 ceroons of Spanish indigo. 



Mr. Geo. S. Riggs : 



Herewith I furnish tables compiled by me from Government 

 works. They show — 

 The imports of indigo from 1st Oct., 1829, to 30th 



June, 1850, 22,490,859 lbs. 



Value, §18,618,379 



The exports (of foreign growth) from 1st Oct.. 



1829, to 30th June, 1850, 3,272,833 lbs. 



Value, $4,025,048 



The exports (of liome growth) from 1st October, 



1829, to 29th June, 1830, 10,663 lbs. 



Value, $7,229 



Imported of growth and manufacture of foreign countries. 



