^2 Bleaching Raw Si!i. — Mathtmatkol Carrefpetidtuce. 



vitriolic acid. And if from curiofity the produfts of feveral of the retorts be received in 

 eight dilTercnt parts, it will be (ten that in fome the acid which pafles firft is the moft 

 concentrated, and gives 20 degrees by the hydrometer ; that the produfts diminilh fuc- 

 ceffively in the progrefs of concentration, till the lalt exhibits fometimes no more than 

 eight degrees ; but that others afford the moft concentrated acid at the beginning and 

 end, while that in the middle of the diftillation is the wcakeft. All thefe produfts mixed 

 together aflbrd a mean refult of 14, 15, or 16 degrees*. 



The hard compaft faline matter in the retort confifts of much Glauber's fait, and a 

 fniall quantity of undecompofed common fait. M. Baume's method of extrafling it is 

 fimple and ingenious. He fills the retort with water, corks it, and inverts it in an open 

 vefl'cl alfo containing water, over which is fixed a board with holes for receiving the 

 neck of the retort. It is proper that the faline mafs (hould be detached, which foon 

 happens in the filled retort, and fullered to Aide down towards the neck before it is placed 

 in the hole of the board. The cork is then taken out, and by that means the water in the 

 retort communicates with that of the open veflel. As the fait dilTolves, the brine flows 

 down, and is replaced by purer water from below, which from its lefs denfity rifes to the 

 uppermoft place in the retort. In this way the evacuation is made in two days without 

 trouble, which could not fafely be effedled in eight or ten days by fuccelTivc filling and 

 emptying the retorts. 



M. Baume concludes his memoir by defcribing the method of giving a bright yellow to 

 filk, whether raw or bleached. For this purpofe ten gros or drams of nitrous acid are to 

 be mixed with one pound of alcohol, and into this a few ounces of filk are to be immerfed, 

 and kept on the water bath at between 30 and 40 degrees of Reaumur, or 100° and 130' of 

 Fahrenheit. The filk acquires a tarnifhed brown colour, and muft be cleared of its acid by 

 walhing in feveral waters, and afterwards fcoured with foap in the ufual manner. When 

 thus cleaned and dry, it has the appearance of gold threads when feen in the fun's light. 

 Different fhades may be given by keeping it a fhorter time in the acidulated fpirit ; all which 

 are equally permanent, and refift wafliing and every other tell:. The author propofes them 

 to be ufed in articles of furniture wrought in defigns which require light and fliade. 



MATHEMATICAL CORRESPONDENCE. 

 In order to accommodate fuch mathematical correfpondcnts as may refide at a diflance 

 from the metropolis, and are difpofed to contributejo this part of the work, the folutions 

 to the queftiocs propofcd in any number of the Journal will be uniformly given the fecond 

 month after their publication ; but it is requefted that they may be fent as early as poflible, 

 that proper time may be allowed to prepare them for infertion. 



QUESTIONS propofed fir Solution. 

 Question III. By Analttjcvs. 

 YY.'ii required to determine the odds agalnft the dealer, at the game of wliift, having all 

 the thirteen trumps in his own hand. 



• For the corrcrpondcnt fpccific gravities fee p. 39 of this Journal. 



6 QuESTIOM 



