Preparation of Acids for Bleaching Raw SIIL 91 



acid in the ufual manner. But as M. Baume's experience led him lo various fimpic mani- 

 pulations and remarks of importance, and more efpecially as he confiders the defcription 

 of this procefs as part of the new art of bleaching fi!k, he has annexed it to his memoir. 



The vitriolic acid obtained by the foregoing procefs being too concentrated, muft be di- 

 luted in the copper bafon as before with river water. It is convenient to add 1 8 ounces 

 of water to each pound of the acid, becaufe tlie marine acid is not wanted in a flate of high 

 concentration. This mixture ought to give 35 or 36 degrees by Baume's hydrometer; 

 which laft anfwers to a fpecific gravity of I.333- When it is cold it may be preferved in 

 bottles for ufe. 



In the next place, four pounds of marine fait dried, becaufe in that ftate it pours befl, Is 

 to be put into a retort of the capacity of five or fix French pints, or Englifli quarts. 

 This may be done by means of a paper funnel, or a long-necked funnel of glafs, which muft 

 enter the body of the retort in order that the neck may remain clean. A number of thefe 

 muft be difpofed on a gallery in two oppofite rows, with the necks properly enclofed and 

 enveloped in fand as ufual. 



A bottle or gauge being provided of fuch a fize as by previous experiment is known to 

 hold four pounds of the vitriolic acid before mentioned ; this quantity of the acid muft be 

 meafured into each of the retorts by means of a curved funnel, the tube of which may 

 pafs into the body, to prevent the acid being fpilled in the neck. If neverthelefs a few 

 drops fhould fall, no inconvenience will follow, as this pure acid is not detrimental to the 

 bleaching procefs. 



The fupports for the receivers are then to be placed, and the receivers applied, each being 

 pierced with a fmall hole. The jundlures are to be made good with pafted paper, and the 

 diftillation begun. A gradual heat is to be applied until the fluid boils gently. The 

 marine acid which firft rifes is volatile and expanfible *, and requires the fmall holes of the 

 receiver to be occafionally opened ; but after one fourth part of the time of diftillation 

 the acid comes over freely, and the vapours ceafe to be elaftic. 



This diftillation lafts two days; but it is pradicable to avoid fitting up the intermediate 

 night. The fire muft be fo managed that the contents of the retort may be very liquid in 

 the evening ; if it begins to thicken, there is reafon to apprehend that it may be too hard 

 the next day ; in which cafe the heat will dilute the concrete matter before it liquefies, 

 and break the containing vefTel. 



Towards the clofe of the dillilLition the matter fwcUs up confiderably. "When this 

 happens, it is proper to'empty the receivers, and raife the retorts, that more fand may flow 

 in beneath them. When the matter is dry, and nothing more comes over, the operation 

 is finiftied. 



Each retort affords five poumls of marine acid, of tlie ftrcngth of 14 or 15 degrees; 

 fpecific gravity 1.114. When the retorts are half cooled, one pound of hot river water is t» 

 be poured into each, and the diftillation hcing relumed affords 24 ounces of the fame marine 

 acid from each retort. 



It is remarkable, that in this procefs fomc of the retorts afford the colourlefs and fomc 

 the yellow acid ; which is an object of no confcquence with regard to the bleaching. The 

 author thinks the yellow colour is owing to a portion of fulphur ftiU remaining in the 



• Tt might be of advantage, even in the large way, to adapt a fiinple pneumatic jppuatus to ccnJenfL ilie 

 mafinc acid air in water, ai is ufual in philofopliical pn celTis. N. 



N 2 vitriolic 



