Penfield and Sperry — Composition of Howlite. 223 



The lime after being ignited to a constant weight and slaked is 

 transferred to a large platinum dish and warmed with water till 

 it becomes of a milky consistency ; it is not necessary to re- 

 move all the lime from the crucible, the latter being put away 

 and used later on. Strong ammonia is poured into the receiv- 

 ing flask of the distilling apparatus described by Gooch, and 

 after conducting the distillation as directed the contents of the 

 receiver are poured into the platinum dish containing the 

 slaked lime, water being freely used in rinsing out the receiver. 

 The dish is then placed on a triangle over the water bath or 

 otherwise gently heated till the volatile products, methyl alco- 

 hol and ammonia, are driven off, which by boiling might cause 

 mechanical loss. When these are removed the contents of the 

 dish can be evaporated to dryness. The dried calcium borate 

 and the excess of lime are now transferred to the crucible in 

 which the lime was weighed, this being easily accomplished by 

 moistening the contents of the dish with water and shoving the 

 bulk of the precipitate into the crucible with a spatula, by rins- 

 ing with a little water and by using a rubber on the end of a 

 glass rod all but a very little of the borate and lime can be 

 transferred to the crucible ; that which sticks too firmly to the 

 dish can be dissolved in one or two drops of dilute nitric acid 

 which is brought in contact with all parts of the dish with the 

 rubber ; the solution is then transferred and rinsed into the cru- 

 cible. The transfer and washing can readily be made by using 

 not over 30 cc. of water which can be contained in an ordinary 

 student's crucible. The evaporation from this point goes on 

 very simply, the borate drying out nicely on the water-bath. 

 By placing the platinum crucible in a large porcelain one and 

 gradually raising the heat to strong ignition the borate may be 

 further dried out without any danger of snapping. The 

 residue is finally ignited over the blast lamp till a constant 

 weight is obtained. 



In slaking the lime we have found it convenient not to add 

 the water directly to the ignited lime, causing danger from ex- 

 cessive heating and mechanical loss, but to place the open 

 crucible on a watch glass containing water and covered with a 

 bell jar : in this way the lime soon slakes and in case of special 

 hurry hot water may be placed in the watch-glass from time to 

 time so that the atmosphere under the bell jar will be 

 thoroughly saturated ; in this way the lime will become so 

 thoroughly slaked in one or two hours that there will be no 

 danger of excessive heating on further addition of water. 



The following results were obtained using in all cases about 

 one gram of crystallized borax and one" gram of lime : B 2 O s in 

 borax 36-55, 3642, 36-58, 36-64, calculated 36'64 per cent. 



Mineralogieal Laboratory, 

 Sheffield Scientific School, April 14, 1887. 



