of Molybdenum and some of its Compounds. 425 



which is exactly requisite to form the salt ; the mixture fused 

 and solidified on cooling into a white crystalline mass, which, 

 on being pressed or agitated under water, fell into a number 

 of acicular crystals. The saline mass dissolved with great 

 difficulty in cold water, and only after a long time in hot. 

 The liquid was evaporated to a very small bulk, but no 

 crystals separated either by heat, nor after standing for three 

 days. The concentrated solution was further evaporated in a 

 platinum crucible in the water-bath, when gradually a white 

 crystalline mass separated, whilst another portion was left as 

 a syrupy liquid. The crystals were collected on a filter and 

 washed with a little water, when the greater portion of the salt 

 redissolved ; it was then dried as quickly as possible by pressure 

 between folds of paper, and finally at a temperature of 176° F. 



The salt appeared to consist, under the microscope, of four- 

 sided prisms; it dissolves readily in water, but with great 

 difficulty after fusion. When heated, it parts with its water 

 of crystallization, melts and solidifies on cooling to a yellowish 

 white crystalline mass. 



Analysis. — 0*4473 grm. salt lost on ignition 0*0203 water, 

 and gave 0*18] 9 sulphate of soda = 0*0796 soda. 



The crystalline salt consists therefore in 100 parts of — 



a. Calc. b. Calc. Found. 



1 at. Soda 389-729 17*092 389729 17*292 17798 



2 at. Molybdic acid 1777*932 77*9/5 1751*658 77718 77*552 

 1 at. Water 112*479 4933 112*478 4990 4-650 



2280*140 100000 2253*865 100*000 100*000 



and the anhydrous salt of — 



1 at. Soda 389729 



2 at. Molybdic acid 1777*932 



2167661 100000 2141-387 100-00 100000 

 Trimolybdate of Soda. — Formula of the crystalline salt 

 NaO, MoO 3 + 7HO. When nitric acid is added gradually 

 to a concentrated solution of molybdic acid in carbonate of 

 soda, no double salt separates, as is the case with the potash 

 salt. When so much acid is added that the liquid exhibits 

 an acid reaction, trimolybdate of soda separates after some 

 time as a bulky precipitate. It crystallizes like the cor- 

 responding salt of potash, but is more soluble in water. The 

 salt dried in the air contains more water of crystallization than 

 the potash salt, which it parts with on being heated to redness ; 

 it melts and solidifies on cooling into a crystalline mass. 



Analysis. — I. 0*618 grm. salt lost at a red heat 0*1253 water 

 and gave 0*1490 sulphate of soda = 0*065 soda. 



II. 0*8467 lost on ignition 0*1725 water. 

 Phil. Mag. S. 3. Vol. S3. No. 224. Dec. 1848. 2 F 



