l66 Ptitificat'wi cf AH alii. — Eau de Luce. 



12. By expofing fuoli alkaline cryftals to a red heat Lii a very clean crucible, they become 

 fufcd ; and, after cooling in proper moulds, aflbrd a lapis cauRicus as white as fuow, and 

 extremely eauftic and deliqucfcent. 



13. As the cryftals and the lixivium, during the length of time required to drain the fait, 

 may frequently become charged with a portion of carbonic acid, it is advifable, in order 

 to avoid this inconvenience as much as pofTible, that the lixivium, as foon as it is brought 

 to the requifite point of faturation, fliould be poured into a natrow-necked bottle, and well 

 clofed therein to cryflallize. After the cryftals are formed, the bottle is to be reverfed, 

 ■without opening, and kept at a temperature rather warm until the cryftals are well dried. 

 During the winter, the liquor, after the firft cryftallization, continues to cryftallize with- 

 out being fubmitted to a new evaporation, provided only that it be expofcd to a tempera- 

 ture fomcwhat colder than tliat wherein the firft cryftals were formed *. 



VII. 



Expiiiments on Eau de Luct. By a Correfpondent . 

 To Mr. Nicholson, Editor of " The Journal of Natural Philofiphy, Chemijlry, and the ArtiT 

 SIS, 



\JbSERVING in your fecond number a paper on the compound called Eau de luce, I 

 here fend vou the refult of fome curfory experiments, which I was induced, for the bene- 

 fit of my female friends, to make fome years fince on this article. You will perhaps your- 

 felf profecute them farther than I have had an opportunity of doing. 



1. Macquer's recipe, and that in the London Pharmacopeia, were both tried ; but neither 

 of them fucceeded. I was however informed by a very intelligent apothecary, that thebcft 

 eau de luce might be, and always was, made without any other ingredient than oil of 

 amber, foap, alcohol and ammoniac: he added, that thofe who are judges of this article 

 dete£t in a moment the prefence of maftic, and efteem fuch as contains it of very little 

 value. The proportions were accordingly varied. Different fpecimens of the oil were 

 ufed — fome of the firft diftillation, others twice reaificd— but with no better fucccfs. — The 

 bed product was too highly coloured. When daflicd againft the fides of the phial, if did 

 «iot flow back uniformly, but prefented a fomewhat greafy appearance, not much unlike 

 that of a common emulfion with oil and an alkali -, and after fome days the oil feparatcd 

 like a cream on the top, and the liquor became fcmi-tranfparent. 



2. Being aiTured from a number of enquiries, that maftic was the moft ordinary bafis of 

 the emulfion, this was alfo tried, and fucceeded tolerably at firft. Tlie milky appearance is 



* Cryftals of cauftic pot-afli may alio be obta'ncd by the fucctflivc evaporation of a folution of the pot-nth 

 of commerce until the appearance of a light pellitle. The firft cryftals which appear arc the alkaline carbonate, 

 or mild alkali, and the latter the pure pot-a)h. In this way the lixivium is reduced into very regular cr)ft.ils, 

 to the very Uft portions of fait which it contains. Half an ounce, the refidue of a folution of fcvcral pounds, 

 ftill affords very regular cryftals. It is even rcmatkable, that the latter crj-ftallizations are formed with infi- 

 nitely more f.icility than the firft. 1 inferted this obfervation in a Memoir on the preparation of the carbonate 

 of pot-a(h for the alkaline mcphitic water of Colbum, which I addreffcd at rhe beginning of 1793 'orhc So- 

 cieui I'hilomatiquc de Paris, and hai in part been printed in L'Efprit dcs Jouroaux for the lame year. Nuic 



of \'an Mons. 



however 



