PUR 



Library at Dublin. This delivery has been f^'t t° ^^^ 

 fevere burthen, and feveral petitions have been prefented to 

 parliament by authors as well as pubhfhers of books to be 

 relieved from it. Thefe petitions were in the feffions of 

 1818 referred to a committee of the Houfe of Commons, 

 which examined many witnefTes on the fubjea, and made a 

 report to the Houfe of the followmg import : 



That it is the opinion of this committee, that it is 

 defirable that fo much of the copyright ad as requires the 

 gratuitous delivery of eleven copies (hould be repealed, 

 except in fo far as relates to the Britith Mufeum, and that 

 it is defirable that a fixed allowance (hould be granted in 

 lieu thereof, to fuch of the other public hbranes as may be 

 thought expedient. , tt r 



That if it (hould not be thought expedient by the Houle 

 to comply with the above recommendation, it is defirable 

 that the number of libraries entitled to claim fuch dehvery, 

 fhould be reftriaed to the Britiili Mufeum, and the libraries 

 of Oxford, Cambridge, Edinburgh, and Dubhn univerfities. 

 That all books of prints, wherein the letter-prefs (hall 

 not exceed a certain very fmall proportion to each plate, 

 (hall be exempted from delivery except to the Mufeum, 

 with an exception of all books of mathematics. 



That all books in refped of which claim to copyright 

 (hall be exprefsly and efFeftually abandoned, be alfo 

 exempted. 



That the obligation impofed on printers to retain one 

 copy of each work printed by them (hall ceafe, and the 

 copy of the Mufeum be made evidence in lieu of it. 



PROPHECY, col. 3, 1. 26, for Wolfton r. Woolilon. 

 Col. 5, 1. 10 from bottom, for Woolafton r. Woolfton. 

 PROPOLIS, 1. 33, add— See Wax. 

 PROPORTIONAL Compass, 1. 2, r. proportional. 

 Col. 2, 1.8, r.fg.i. Plate I. of Proportional Compajes. 

 Col. 5, 1. 10 from bottom, infert Jig. 10. Col. I, 1. 30, r. 

 fig. II. 



PROVERB, col. I, 1. jy from bottom, for print r. 

 fruit. 



PROVIDENCE, Nethek, 1. i, r. Delaware for 

 Luzerne. Col. 2, 1. 2, r. Delaware. 



PRUSSIC Acid, in Chermjlry. See Cyanogen. 

 PUFF-Ball, 1. 2, add — and Tulostoma. 

 PULASKI, for PuLASNi, 1. 2, add — of whom 528 were 

 (laves in 18 10. 



PULTNEY, a townihip of Belmont county, in Ohio, 

 having 645 inhabitants. 



Vol. XXIX. 



PUR AN A, col. 3, 1. 6, for Vari(hta r. Vafi(hta. 



PURPURIC Acid, in Chemlpy. The name of an acid 

 principle recently difcovered by Dr. Prout ; produced by 

 the aftion of nitric acid upon the lithic or uric' acid. The 

 beautiful purple fubftancc produced by the aftion of the 

 nitric acid and heat upon lithic acid, has been long known 

 to ehemifts. This purple fubftanee is a compound of the 

 acid in queftion and of ammonia. This acid, which may be 



P Y R 



likewife formed from the lithic acid by chlorine and iodine, 

 polfeffes the remarkable property of forming beautiful 

 purple compounds with the alkalies and alkaline earths. 

 Hence the name of purpuric acid has been adopted by 

 Dr. Prout, which was fuggefted by Dr. Wollafton. 



Purpuric acid may be feparated from the purpurate of 

 ammonia above-mentioned, by the fulphuric or muriatic 

 acids. It ufually exifts in the form of a light yellow or 

 cream-coloured powder. It is exceedingly infoluble in 

 water, and confequently poffeffes no tafte, nor alfefts 

 litmus paper, though it readily decompofes the alkaline 

 carbonates by the aniftance of heat. It is foluble in the 

 ftrong mineral acids and in alkaline folntions, but not in 

 dilute acids in general. It is infoluble in alcohol. When 

 expofed to the air it affumes a purple colour, probably by 

 attratling ammonia. Submitted to heat it is decompofed, 

 and yields carbonate of ammonia, pruffic acid, and a little 

 fluid of an oily appearance. 



The alkaline purpurates, as before obferved, all form 

 folutions of a beautiful purple colour. They are capable 

 of cryftallizing, and their cryftals poflefs fome remarkable 

 properties. The purpurate of ammonia cryftallizes in qua- 

 drangular prifms, which when viewed by tranfmitted light 

 appear of a deep garnet -red, but by reflefted light two of 

 the oppofite furfaces appear of a beautiful green, while 

 the other two retain their natural red colour. This 

 curious property feems to be poffeffed by the other alkahne 

 purpurates. Tlie metallic purpurates are in general 

 remarkable for their folubility, and the beauty of their 

 colours. The purpurate of zinc is of a beautiful gold- 

 yellow, the purpurate of tin of a pearly-white. The other 

 purpurates are all more or lefs of a red colour. 



Dr. Prout thinks it probable, that this acid forms tlie bafis 

 of many animal and vegetable colours. The pink colour 

 of the fediment in the urine of fever feems to be owing to 

 the purpurate of ammonia. Dr. Prout alfo thinks, that 

 fome of its falts might be ufed as paints, and alfo for dye- 

 ing, as they appear to poffefs ftrong affinities, efpecially 

 for animal fubitances. See Philofophical Tranfadions for 

 1818. 



PURSHIA, in Botany, fo called in juft commemoration 

 of Mr. Frederick Purfli, author of the rich Flora Americit 

 Septentrionalis. — De Cand. Tr. of Linn. Soc. v. 12. 157. — 

 Clafs and order, Jcofandria Monogynia. Nat. Ord. Senticofa, 

 Linn. Rofacee, Juff. 



Eff. Ch. Calyx five-cleft. Petals five. Capfule fupe- 

 rior, oblong, of one cell, burfting at one fide. Seed foli- 

 tary, ere ft. 



1. F. triilentata. Downy Pur(hia. De Cand. (Tigarea 

 tridentata ; Purlh 333. t. 15.) — In the meadows of the 

 Rocky-mountains, and on the Columbia river, flowering in 

 July. A much branchedyZiru^, with wedge-fhaped, crowded 

 leaves, three-lobed at the extremity, and folitary, terminal, 

 yeWow Jlo'wers, nearly the (ize of Hawthorn. 

 PYMATUNING, 1. 3, ;•. 379. 



PYRAMID, col. 2, 1. 36, dele and charafter and feet. 

 PYRO ACETIC Spikjt, in Chemi/lry. See Acetic 

 Aciii. 



