BORATE DISTRICTS OF PERU. 119 



the history of nitrate and its varieties, also that it contained chrome and 

 iodine. Of chrome it is in very small quantities ; but as to the iodine, Ulex, 

 of Hamburg, got six-tenths per cent, out of a mixture of caliches. Hayes, 

 of New York, the same. Ulex obtained one-half to one per cent, from the 

 motber waters. I suspect that in some varieties the per centage of iodine 

 is greater than given by Ulex. Sea water only contains one-millionth part 

 of iodine ; that found in the nitrate has its origin, I conceive, from mineral 

 iodides and iodates. When the caliche has a yellow or orange colour, it is 

 called azufrado and canario. The mother waters at Negreros are sometimes 

 blood red. I once supposed that this colour was owing to iodine ; I now 

 think it is from chrome. Bromine has been found in the caliches. 



About 1853, several vessels were sent to the West Coast of Africa, in the 

 hope of being able to ship nitrate of soda, but the saline matter met with 

 there proved to be salt. The vicinity of the Dead Sea has been examined 

 for nitrates, but none as yet found. Nitrate of soda is well known as a 

 fertiliser, and is used extensively in the arts. It has been converted into 

 nitrate of potash for the gunpowder makers, but its employment has not 

 been patronised in consequence, it is said, of its deliquescence. I am 

 informed that pure nitrate of soda is not deliquescent — is it that such 

 property is owing to chloride of calcium the imported nitrate always 

 contains ? 



Test for Nitrate of Soda. — The cateador or caliche-hunter easily 

 distinguishes nitrate by the taste, which is bitter and cooling ; salt is merely 

 saline. A delicate test is the following, which will show if there be only 

 2 per cent. : — Add sulphuric acid to a portion in a tube, when, if nitrate be 

 present, red fumes will appear. Salts of soda are distinguished from salts 

 of potash, the soda giving no precipitate with muriate of platina. Hofstetter 

 is said to have found 0.43 nitrate of potash in a sample of refined nitrate 

 from Tarapaca. 



I will now give some details of my own examination of the Pampa de 

 Tamarugal, where it principally exists, and in large quantities. Leaving 

 the Noria and ascending the steep side of its hollow, our course lay east by 

 south, over undulating country, between high mountains, some giving off 

 very large quantities of detritus ; descending a ravine, and approaching the 

 Pampa de Tamarugal, we came upon nitrate caliches at the Binconada, and 

 descending a little lower, an extensive salar is entered, having on its west 

 margin considerable tracts of nitrate caliches. A few tamarugo* and 

 algarobo f trees are seen ; but, excepting these, a salt desert and arid plain 

 occupies the foreground, and far away to the east are the mighty Andes. 



On the eastern margin of the Salar, in particular, as well as in it, and 



* Baimundi says it is a Prosopis, or it may be a new genus. 



f Prosopis dulcis. Seemann calls the algarobo, of Panama, Hymenaea splendida ; that 

 of Peru, Prosopis horrida ; that of Chile, P. siliquastrum, In Tarapaca the Tamarugo 

 is sometimes called Algarobilla ; its pods are round, one to two inches long. The pods 

 of the Algarobo are eight to nine inches long, and contain saccharine matter. The 

 Tara is of the family of Mimosa, it yields much tannin, the pods are flat. 



