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LVI. Additional/ Directions and Improvements in the Process for 

 the Manufacture of Artificial Tourmalines. Bij William 

 Bird Herapath, Esq., M.D. Lond.^ 



IN the last November Number of this Journal the author gave 

 a formula for the production of these crystals of large size, 

 so as to be available for optical piirposes. 



That formula succeeds very well when the temperature of the 

 atmosphere in the apartment is 65°, and likely to be maintained 

 at this point for three or four hours, falUng gradually to 45° 

 Pahr. in the course of the night. Under these circumstances 

 it is rarely the case that some large plates are not discovered in 

 the morning. These should be at once secured or they will 

 re-dissolve or sink, and thus be lost. 



When the tem])erature does not fall bdow 50° or 55° Fahr. 

 a different formula is necessary. Less spirit must then be 

 employed, in order to render the compound less soluble in the 

 menstruum. 



Formula No. 2 may now be used most successfully. 



(2) Take of disulphate of quinine 100 grains, ^^ 



acetic acid (1-042) 4 fluid ounces, ;j 



rectified spirit (0-837) 1 fluid ounce, ."j 

 spiiituous solution of iodine 1 fluid drachm. 



The crystals are produced more quickly by this formula than 

 by the previous one; and in three or four hours must be re- 

 moved, or the mother-liquid will quickly redissolve them. 

 j\Iauy of the larger crystals become too heavy to float any longer 

 and fall to the bottom of the flask, from whence they are not 

 easily removed ; still by the exercise of patience and some in- 

 genuity they may be recovered, and fully repay for the trouble 

 of cutting off the top of the flask, &c., by producing a field 

 wholly devoid of violet light upon crossing two plates, especially 

 when examined by daylight. 



Formula No. 3. — I have recently succeeded in making these 

 crystals of large size, by replacing the spirit of wine in No. 2 

 formula, by an equal quantity of hypouitric jether (sweet nitre). 

 There is some advantage in using this solvent, as the crystals 

 remain even for a week floating on the stxrfacc, without showing 

 the least appearance of disintegration. 



It is frequently the case in this experiment, that the free 

 iodine disappears very readily; the solution becoming nearly 

 colourless — under these circumstances, the compound does not 

 form. If the temperature employed be too elevated, this is 

 almost certain to occur ; of coui-se it is only necessary to add a 



* Comm'.micatofl by the Author. 



