224 



Varieties. 



[FEB. 



themselves destroyed ; while the salts that 

 are attached to them are left behind. 

 Hence the more foul the water, the more 

 complete the depuration ; and it is on this 

 principle that the popular opinion of the 

 peculiar fitness of Thames water for being 

 used at sea may be explained ; its extreme 

 impurity inducing a sufficient degree of fer- 

 mentation to effect the removal of all those 

 substances which might occasion any future 

 renewal of that process. 



Atomic weight of Mercury. In a recent 

 examination of the powder supposed to be 

 a protoxide of mercury, the attention of an 

 experienced American chemist, was turned 

 to the subject of the atomic weight of mer- 

 cury ; and upon applying to some of its 

 combinations the generally received theory 

 that binary compounds are more difficult of 

 decomposition than ternary, he was led to 

 the conclusion that its equivalent number 

 has been misstated by chemical writers. 

 The protosulphuret and protochloride are 

 both more easily decomposed than the com- 

 pounds containing double the proportion of 

 heir respective electro negatives. The only 

 cyanide of mercury is now considered as 

 containing two atoms of cyanogen. The 

 protoxide, it is believed, exists only in com- 

 bination with acids. He has very frequently 

 decomposed several of the protosalts of mer- 

 cury with alkalis, and the resulting powder 

 has uniformly contained metallic globules, 

 either visible to the naked eye or easily 

 rendered so by a slight degree of friction 

 with the finger; the pressure attending 

 which could only have brought already ex- 

 isting uncombined particles within the 

 sphere of each others attraction. When 

 calomel (protochloride of mercury) is de- 

 composed by an alkaline solution, if the 

 latter be cautiously dropped upon it, a red- 

 dish powder is at first apparent (a careful 

 repetition of this experiment has placed its 

 accuracy beyond a doubt. On calomel, 

 prepared by precipitation from a solution of 

 crystallized protonitrate of mercury with 

 muriate of soda, which was repeatedly 

 washed with warm distilled water, with 

 solution of muriate of ammonia, and with 

 warm alcohol, he dropped a small quantity 

 of potass water, a reddish powder was very 

 distinctly observable. When sufficient al- 

 kali was added to decompose all the calomel, 

 the powder was of a brownish black colour ; 

 and when dry, contained visible globules of 

 metal. This shows the fallacy of one of 

 the reputed tests of the purity of calomel.) 

 This fact and the subsequent evidence of 

 the existence of metallic mercury in the 

 powder, may serve to explain each other. 

 A muriate of the alkali is formed at the 

 expense of a portion of water, and the oxy- 

 gen being left to the free exercise of its 

 affinity, forms with half of the metal a 

 binary compound, the red oxide through 

 which the remaining proportional of mer- 

 cury in a state of extreme comminution is 



mixed. The powder will be found capable 

 of amalgamating gold, and the uncombined 

 metal may be rendered evident by friction, 

 percussion, or elevation of temperature, or 

 by pouring upon it a minimum quantity of 

 diluted acetic acid. The supernatant liquor 

 will contain peracetate. More conclusive 

 evidence of an error in the atomic weight 

 of any body, could not be adduced. An- 

 nexed is a table of the corrected atomic 

 weights of a few of the mercurial combi- 

 nations : 



Preparation of Hartshorn Jelly. The 

 following process is due to a French che- 

 mist, M. Ferrez: four ounces of rasped 

 hartshorn are to be steeped in eight ounces 

 of water, acidulated with sixty grains of mu- 

 riatic acid for ten minutes, and then washed 

 carefully in two or three waters. It is theft 

 to be boiled with fresh water for half an 

 hour, pressed through a cloth, and the liquid 

 filtered while hot. This fluid is the jelly, 

 which being qualified by sugar or other in- 

 gredients, and boiled slightly, gives, upon 

 cooling, a perfectly clear and good jelly for 

 the table. 



The Progress of Steam That a steam 



carriage could be produced was well known 

 to every engineer, the object to be obtained 

 was to produce a machine which, when 

 every thing connected with it was consi- 

 dered, should be less expensive than a ve- 

 hicle drawn by horses ; whether this is 

 finally obtained is yet to be seen. But the 

 results which have appeared, from a compa- 

 rative trial near Liverpool, of certain loco- 

 motive engines, seem to have given rise to 

 a new question whether or not a force ca- 

 pable of producing a velocity (on a rail-road 

 certainly) of 32 miles in the hour, may not 

 be applied by means of rotatory vanes, to 

 raise and direct a body in the air or at any 

 rate guide a balloon. The success of such 

 an attempt is by no means more chimerical 

 than many projects which have been brought 

 to bear at the present time, would have ap- 

 peared half a century since ; and though we 

 are far from thinking that the element of 

 air, like the other elements, will be subjected 

 to the power of man, still it is by no means 

 improbable that material benefits may accrue 

 from the attempt. 



