J. M. Ordway — Waterglass. 473 



Art. XLIII. — Waterglass ; Part YI ; by John M. Ordway. 



[Continued from vol. xl, p. 190, 1865.] 



The urgent duties of a busy life have interrupted this inves- 

 tigation for many years, but latterly changed circumstances 

 have allowed the work to be resumed, and now something may 

 be added to what has already been set forth. 



It has been shown that alcohol throws down the silicates of 

 potassium and sodium from their solutions, retaining at the 

 same time a portion of their base. Acetone and methylic alco- 

 hol are found to answer equally well as precipitants. Some- 

 times neutral saline solutions may be advantageously used for 

 the same purpose. And most of such deposits, as well as pre- 

 cipitated silicates of the other metals and hydrated silicic acid 

 itself, can be nearly freed from the mother liquor by folding 

 the drained curd in closely woven cotton cloth and subjecting 

 to strong pressure applied gradually. The cloth can be peeled 

 off from the cake with very little loss. 



Of course the water in the cake is partly water of hydration 

 and partly absorbed mother liquor ; and how much there is 

 of each cannot always be determined. But when a chloride, 

 incapable of forming a basic salt, has been used in the precipi- 

 tation, the amount of retained mother liquor may be ascer- 

 tained by comparing the percentage of chlorine in the pressed 

 curd with that in the remaining liquid. 



Experiments 3a, ~b given below will serve to show what dif- 

 ferences there may be between the gross analyses and the net 

 composition obtained by deducting the small quantities of solids 

 due to retained mother liquor. But the differences are slight, 

 and for our present purpose perfect exactness has been deemed 

 unnecessary. Therefore, except when otherwise specified, the 

 gross analysis is given ; and for the sake of convenience and 

 brevity, the results are expressed approximately in empirical, 

 dualistic formulas, the water of combination being left out of 

 account. 



Silicates of Lithium. — These are sometimes spoken of as 

 being insoluble in water. But this really applies only to the 

 anhydrous compounds such as are formed by fusing the car- 

 bonate with silica. In fact when we mix weak solutions of 

 sodium waterglass and lithium chloride there is no precipita- 

 tion. Hence either no exchange of bases takes place or the 

 lithium waterglass remains dissolved. But when strong solu- 

 tions are put together an abundant deposit is formed, the nature 

 of which is shown by the following experiments : 



1. 13 grams of a 31 p. c. solution of lithium chloride added to 

 100 cubic centimeters of a solution containing- 10 £. of Na o 3SiO„ 



