^0 Method of rejioring IVrlling. 



the atmofphere. A few drops of fulphuric acid let fall iipom 

 it, produced aa efFervefcence, and white clouds of ox. mu- 

 riatic gas efcaped, as was very evident from the fmell, and 

 from the tefts generally ufed to dete£l the prefence of this 

 gas. 



The difcovery of Mr. Lambe is the bed which has been 

 made for many years. 



^lETHOD OF RESTORING WRITING WHICH HAS 

 BEEN EFFACED BY OXYGENATED MURIATIC ACID. 



As the art of effacing writing by means of this acid might 

 give rife to a<?t3 of fraud, the following letter from the Secre- 

 tary-general of the French Minifter of the Interior has been 

 lately publillied in the official paper the Aloniteur : it is 

 addrefled to the editor: — " C. Giiietand, apothecary of the 

 Grand Hofpital of Humanity, the ci-devant Hoiel-Dieu, hae 

 difcovered the means of reviving writing effaced by oxygen- 

 ated muriatic acid *. His proccfs has been examined by 

 chemifts, who have found, that it is eafy, as well as fpcedy 

 in its effect, arid that it deferves to be known. 



" The minifter, therefore, has determined that it fhall be 

 made known by being printed, I herewith tranfmit you an 

 account of the proccfs ; and I requeft that you will infcrt it 

 in your next number." 

 « iv%. 26, 1800. (Signed) F. DESPORTES." 



The fulphure of ammonia and the prufiiat of potafli are the 

 two fubftances which C. Guitand prefers for reviving writing 

 effaced by oxvgenated muriatic acid. The dlfagreeable fmell 

 of the fulphure of anmionia will, no doubt, prevent many per- 

 fons from employing it: it has, however, this advantage, that 

 it does not (lain the paper, and that it makes the writing re- 

 appear when (imply expofed to its vapour in a clofe veffel or 

 under a bell-glafs. But to produce this effe6l more fpeedily, 

 it will be beft to pour a few drops of it into water, and to dip 

 the paper in it : the effaced writing foon re-appears of a dark 

 brown colour, and exceedingly legible. 



* The proccfs for tfTiu ing writing by this acid may be feen in the 

 Phiiwfophical Alagaiiue, Vol, II. p. 4S. 



Th« 



