Penfield — Chemical Composition .of Hamlinite. 315 



ignition, using a weighed quantity of lime to retain the 

 fluorine.* The air-dry powder lost only 0*16 per cent by 

 heating to 100°, and the water was not expelled until the min- 

 eral was heated nearly to redness, thus indicating the presence 

 of hydroxyl. 



The results of the analysis are as follows : 



Average. Ratio. 



28 92 2892 -204 1-00 



1-55 



P 2 5 .--. 







A1 2 3 ..- 



32-29 



32-30 



Fe 2 3 ___ 





•90 



SrO _ 



18-33 



18-53 



BaO 



4 10 



3-89 



H 2 .... 







F 



1-93 





Si0 2 



•96 





K 2 0._._ 





•34 



Na 2 ... 





•40 



11-93 12-07 



Oxygen equivalent of fluorine, 



28-92 



•204 



3230 



•316 



•90 





18-43 



•178 



4-00 



•026 



12-00 -r-i 



= 1-333 



1-93 



•102 



•96 





•34 





•40 





100-18 





•81 





•204 1-00 

 1-435 703 



99-3? 



The ratio of P 2 5 : A1 2 3 : (Sr+Ba)0 : (OH+ F) is very 

 nearly 1 : 1*5 : 1 : 7, which gives the formula Al 3 Sr(OH) 7 F 2 7 or 

 better [Al(OH) 2 ] 8 [SrOH]P 2 7 , where strontium is partially 

 replaced by barium and hydroxyl by fluorine. 



By the method of preparing the mineral for analysis traces 

 of adhering feldspar and mica could not be wholly avoided, 

 and, although the small quantities of Fe 2 3 and alkalies may 

 belong partly to the hamlinite and partly to impurities, these 

 have been neglected in making the calculations. If the alka- 

 lies together with their equivalent of A1 2 3 (1*06 per cent), the 

 Fe 2 3 and the Si0 2 , in all 3*62 per cent, are deducted from the 

 analysis and the remainder calculated to one hundred per cent, 

 the results are as given below, where they are compared with 

 the theoretical composition, where Sr : Ba = 7 : 1 and OH :F= 

 13:1. 



Found. Calculated. 



P 2 5 30-20 30-31 



AJ 2 3 __ 32-67 32-65 



SrO 19-25 19-29 



BaO... 4-18 4-08 



H 2 _. 12-53 12-48 



F _ 2 01 2-04 



100-84 100-85 

 0=F._- '84 -85 



* This Journal, xxxii, p. 109, 1886. 



