lxii GENERAL SUMMARY OF SCIENTIFIC AND 



water than sodium chloride ; hence when a concentrated so- 

 lution of salt is saturated simultaneously by ammonia and 

 carbonic-acid gases, sodium bicarbonate separates from it. 

 The success, commercially, of the process, arises from the 

 skill and ingenuity with which the by-products are worked 

 over. To decompose sufficient salt to produce 5000 kilo- 

 grammes of sodium carbonate would require, for example, in 

 one operation, 5000 kilogrammes of the ammonia salt; while 

 by a skillful rotation the production of 5000 kilogrammes of 

 sodium carbonate a day only requires 250 kilogrammes per 

 day of the ammonia salt. 



The French Academy have devoted considerable time to 

 a discussion of the use of lead in household economy. M. 

 Fordos presented a paper showing that while potable waters 

 containing carbonic acid do convert the lead into an insoluble 

 carbonate deposited on the inside of the tube, yet that danger 

 in the case arises (l) from the fact that this coating, being 

 mechanically detached, may be introduced into the system; 

 and (2) from a subsequent reaction between this carbonate 

 and the chlorides and sulphates contained in the water, pro- 

 ducing soluble sulphato or chloro carbonates. He also 

 warns the public against the use of lead shot for cleansing 

 bottles, having been told by a maker of wine-casks that the 

 discovery of bottles in which such shot had been carelessly 

 left was of daily occurrence. The danger is, of course, in- 

 creased when the wine is put into such bottles, the shot not be- 

 ing removed. He recommends that the lead shot be replaced 

 by clippings of iron wire, four or five millimeters long, Nos. 

 16-18 for large, and Nos. 20-22 for small bottles. 



Salvetat has reported favorably to the Societe d'Encou- 

 ragement upon M. Constantin^s nevv pottery glaze, consisting 

 essentially of sodium silicate, though containing also some 

 lead. The frequent poisoning caused by the lead glazing or- 

 dinarily employed causes M. Salvetat to regret that M. Con- 

 stantin had not gone a little further, and produced a glaze 

 entirely free from this deleterious metal. 



The Terre Noire Iron Company has patented a process 

 for manufacturing cheaply an iron rich in manganese (ferro- 

 manganese), to replace the Spiegeleisen now so necessary in 

 the manufacture of Bessemer or Siemens -Martin steel. It 

 consists in treating in the high furnace blocks made up of 



