294 Dr. Anderson oh the Xatro-Buro-Cakite. 



The Natro-Boio-Calcite is found in the nitrate of soda beds of the 

 province of Tarapaca in Peru, and is known to the natives by the name 

 of Tiza. It occurs in rounded masses, varying from the size of a hazel- 

 nut to that of an egg. Externally these fragments have a dull and 

 dirty appearance, but when broken across they are found to be formed 

 of a series of interlaced needles of a brilliant white colour and silky 

 lustre. These crystals were extremely minute in all the pieces I have 

 examined, but the specimen analyzed by Ilaycs was composed of prisms 

 a quarter of an inch in length. According to Ulex, crystals of brogni- 

 artine are invariably present in these masses, but in all those I ex- 

 amined only one small crystal of that mineral was found. 



The qualitative analysis indicated the presence of boracic and sul- 

 phuric acids, lime, soda, water, siliceous sand, and traces of chlorine. 

 Ulex found also traces of nitric acid, but that I examined contained 

 none. I have also been informed that iodine has been observed in it 

 to the extent of 1'6 per cent., but a careful examination failed to detect 

 it in this specimen. The method of analysis adopted was similar to 

 that of Ulex. The water was determined by ignition, and the result- 

 ing mass dissolved in hydrochloric acid ; the siliceous matters separated 

 by filtration, and the sulphuric acid determined in the fluid. Another 

 portion was treated with hydrofluoric acid, so as to expel the whole of 

 the boracic acid in the state of fluoride of boron. The residual mass 

 was then treated with sulphuric acid to convert the fluorides into sul- 

 phates, and the excess of sulphuric acid expelled by heat, the residue 

 being moistened with ammonia and again ignited, so as to ensure 

 absolute neutrality. The mixed sulphates of lime and soda were 

 weighed, and the quantities of lime and sulphuric acid being determined 

 in the ordinary way, the difl"erence gave the amount of soda. The 

 results were — 



Water, 2546 



Boracic acid, 47 '25 



Lime, 1598 



Soda 0-45 



Sulphuric acid, 9*88 



Chlorine, trace. 



Sand, 0-98 



lOO'OO 



This analysis gives results which accord very closely with those of 

 Ulex, excepting that previous to his analysis be boiled the mineral with 

 water, so as to extract the nitrate and sulphate of soda which he had 

 detected in it, and which are obviously a mechanical mixture, and not 

 essential to the constitution of the mineral. This was not done in my 

 case, as the analysis was made for commercial purposes, and I was 



