Cleaning and Whitening Prints or Engravings. Q6l 



This procefs, however, is not fo generally followed as it 

 ought lo be, chiefly hecaufe the preparation of the oxygen- 

 ated muriatic acid is attended with more trouble than fome 

 people will take, arid hecaufe it is fometimes difficult to pro- 

 cure the acid ready made. This confide ration induced M. 

 Fabbroni to make known the following procefs, which is 

 extremely eafy, and may be put in practice by any one. 



Half fill a glafs bottle with a mixture compofed of I part 

 of the red oxyd of lead, or minium, and 3 parts of the mu- 

 riatic acid ; and having doled the mouth of the bottle with 

 a glafs ftopper, put it in a cool place, notexpofedto the light. 

 A certain heat will then be produced, which is an indica- 

 tion that new combinations are formed. The oxyd of the 

 lead abandons a confiderable portion' of its oxygen, which 

 remains combined with the liquor * ; the latter then ac- 

 quires a beautiful gold colour, and affumes the odour of the 

 oxygenated muriatic acid. It holds in folution a fmall por- 

 tion of the lead, which does not in the leaft injure its effect f. 

 It is neceflary that the bottle fliould be of ftrong glafs, and 

 that the ftopper be well fecured, in order to prevent the 

 claftic vapour which rifes from forcing it out. "When you 

 employ the liquor thus prepared, take a large pane of glafs, 

 and raife a kind of border- of white wax around its edge, 

 about two inches in height, and every where equal. By 

 thefe means you form a fort of trough, into which put 

 Ihe prints, and pour over them a little frefh urine, or water 

 mixed with a portion of ox-gall. At the end of thite or four 



* Where the oximuriat of pot-afh can be had, the procefs recom- 

 mended by Mr. Cruickfliank, of Woolwich Hofpital, will be found neater 

 than the one here propofed. If the oxygenated muriat of pot-am be 

 (imply added to the muriatic acid, diluted with about an equal bulk of 

 water, the fait is llowly decompofed, and the acid converted into the oxy- 

 genated acid. About 1 drachm of the fait, if pure, is found to be fuffi- 

 cient for three ounces of the dilute acid. Edit. 



•J- If this be a fa£t, the portion of lead held in folution muft be final! 

 indeed — otherwifc it mould be partially revived in a length of time, and 

 produce blacknefs. Edit. 



S 3 days 



