558 BOOK XII. 



salt liquor, the Spaniards think, as Pliny writes^, that the wood itself turns 

 into salt. Oak is the best wood, as its pure ash yields salt ; elsewhere hazel- 

 wood is lauded. But with whatever wood it be made, this salt is not 

 greatly appreciated, being black and not quite pure ; on that account this 

 method of salt -making is disdained by the Germans and Spaniards. 



The solutions from which salt is made are prepared from salty earth or 

 from earth rich in salt and saltpetre. Lye is made from the ashes of reeds 

 and rushes. The solution obtained from salty earth by boiling, makes salt 

 only ; from the other, of which I will speak more a Uttle later, salt and salt- 

 petre are made ; and from ashes is derived lye, from which its own salt is 

 obtained. The ashes, as well as the earth, should first be put into a large 

 vat ; then fresh water should be poured over the ashes or earth, and it should 

 be stirred for about twelve hours with a stick, so that it may dissolve the 

 salt. Then the plug is pulled out of the large vat ; the solution of salt or the 

 lye is drained into a small tub and emptied with ladles into small vats ; 

 finally, such a solution is transferred into iron or lead caldrons and boiled, 

 until the water having evaporated, the juices are condensed into salt. The 

 above are the various methods for making salt. (Illustration p. 557.) 



Nitrum^ is usually made from nitrous waters, or from solutions or from 

 lye. In the same manner as sea-water or salt-water is poured into salt-pits 

 and evaporated by the heat of the sun and changed into salt, so the nitrous 

 Nile is led into nitrum pits and evaporated by the heat of the sun and con- 



*Pliny XXXI., 39-40. " In the Gallic provinces in Germany they pour salt water 

 " upon burning wood. The Spaniards in a certain place draw the brine from wells, which 

 " they call Muria. They indeed think that the wood turns to salt, and that the oak is the 

 " best, being the kind which is itself salty. Elsewhere the hazel is praised. Thus the char- 

 " coal even is turned into salt when it is steeped in brine. Whenever salt is made with wood it 

 " is black." 



*We have elsewhere in this book used the word " soda " for the Latin term nitrum, 

 because we believe as used by Agricola it was always soda, and because some confusion 

 of this term with its modern adaptation for saltpetre (nitre) might arise in the mind of the 

 reader. Fortunately, Agricola usually carefully mentions other alkahs, such as the product 

 from lixiviation of ashes, separately from his nitrum. In these paragraphs, however, he has 

 soda and potash hopelessly mixed, wherefore we have here introduced the Latin term. 

 The actual difference between potash and soda — the nitrum of the Ancients, and the alkali 

 of Geber (and the glossary of Agricola), was not understood for two hundred years after 

 Agricola, when Duhamel made his well-known determinations ; and the isolation of sodium 

 and potassium was, of course, still later by fifty years. If the reeds and rushes described 

 in this paragraph grew near the sea, the salt from lixiviation would be soda, and likewise 

 the Egyptian product was soda, but the lixiviation of wood-ash produces only potash ; as 

 seen above, all are termed nitrum except the first. 



Historical Notes. — The word nitrum, nitron, nitri, neter, nether, or similar 

 forms, occurs in innumerable ancient writings. Among such references are Jeremiah (11., 22) 

 Proverbs (xxv., 20), Herodotus (11., 86, 87), Aristotle {Prob. i., 39, De Mirab. 54), Theo- 

 phrastus {De Igne 435 ed. Heinsii, Hist. Plants in., 9), Dioscorides (v., 89), Pliny (xiv., 26, 

 and XXXI., 46). A review of disputations on what salts this term comprised among the 

 Ancients would itself fill a volume, but from the properties named it was no doubt mostly 

 soda, more rarely potash, and sometimes both mixed with common salt. There is every 

 reason to believe from the properties and uses mentioned, that it did not generally com- 

 prise nitre (saltpetre) — into which superficial error the nomenclature has led many translators. 

 The preparation by way of burning, and the use of nitrum for purposes for which we now 

 use soap, for making glass, for medicines, cosmetics, salves, painting, in baking powder, 

 for preserving food, embalming, etc., and the descriptions of its taste in " nitrous " waters, — 

 all answer for soda and potash, but not for saltpetre. It is possible that the common occur- 

 rence of saltpetre as an efflorescence on walls might naturally lead to its use, but in any 

 event its distinguishing characteristics are nowhere mentioned. As sal-ammoniac occurred 



