Chemistry and Physics. 281 



the evaporation can be conducted with very little loss. This is accord- 

 ingly the process recommended by the inventors of the freezers above 

 mentioned. A Committee of the Society for Encouragement of the Arts 

 at Paris, reported favorably upon the apparatus of M. Goubaud. The 

 salts are not named, but are undoubtedly those above mentioned. To 

 make one pound of ice, about five pounds of the salts with five pints of 

 water were required — the duration of the process fifteen to eighteen min- 

 utes. The loss of the salts amounted to not quite one per cent., cost 

 1'7 cents ; the fuel for evaporation, charcoal, at Paris prices, four cents, 

 making the pound of ice cost 57 cents or say 6 cents. The chief 

 part of the expense being for the fuel, it is manifest that ice may be 

 made most cheaply where wood or coal costs least. A part of the 

 fuel may be saved by evaporating as far as possible by the heat of the 

 sun; hence the hotter and drier the atmosphere, cceleris paribus , the 

 less the cost of the ice. 



In the report quoted above, the committee admit that by these and 

 other expedients the cost may be greatly reduced from that named, 

 which it must be remembered is for the city of Paris where fuel is very 

 dear. In most of the southern and southwestern States, {he price of 

 iuel is such as to reduce the cost of evaporations to less than one cent 

 for one pound of ice, being in all two and a half to three cents per 

 pound. The loss in the salts could easily be avoided, wholly or in part, 

 and this would reduce the price to less than two cents. But this is not 

 all. The cold liquor resulting from the solution of the salts may be 

 advantageously employed in cooling provisions, &c, and in the con- 

 trivances for this purpose, are found the chief difference between the 

 French freezers and those in common use. 



It is hardly necessary to state that the widely circulated story that ice 

 can be produced artificially for one dollar per ton, must be an utter ab- 

 surdity. The naturally formed ice costs at least as much as this by the 

 lime it is housed, and that formed artificially must require as much if 

 not more handling. 



Sulphate of soda may be added to the mixture of salammoniac and 

 flitre, but we know of no experiments upon its use on the large scale. 



G. C. SCHAEFFER. 



12. Composition of the Tungstates; by A. Laurent, (Journ. de 

 "harm, et de Chim., Jan., 1848.) — A study of the properties of these 

 salts has led to the conclusion that they do not all contain the same acid. 

 H. Laurent enumerates five or six of these acids which form ammonia- 

 ca ' salts having different properties, and which when calcined leave an 

 anhydrid having the same per-centage composition, yet are capable each 

 one of regenerating its own acid or ammonia salt. 



The first type is the tungstic* W0 4 M^ with or without aq. To this 

 type belong most of the insoluble tungstates : also the yellow acid 

 W0 4 H 2 obtained by treating wolfram with aqua regia. This acid is 

 Ve «7 soluble in ammonia, but on evaporation the ammonia salt of the 



aext type is formed. 



2d type, Paratnngstate. This includes most of the common bi- 

 tarigstates ; the anhydrid is W 4 O l2 , as that of the last is W0 3 . 



* We retain M. Laurent's notation M 2 H 3 Ka 2 and being equal to M, H, Ka 

 Second Series, Vol. VII, No. 20.— March, 1849. 36 



