302 Dr. Schafhaeutl 07i the Different Species of 



duum of the Swedish iron will assume the same appearance as 

 the English, and so in the reverse case; this circumstance ex- 

 plains why anchors made of English iron, although tougher 

 than those made of Swedish iron, are almost twice as soon 

 destroyed by the action of sea water. 



The same rule holds good, when iron, with other chemical 

 agents, is treated in the dry way. For instance, at the same 

 degrees of heat as those in which malleable iron of the specific 

 gravity T'^ has combined with the greatest quantity of carbon 

 necessary for it to become liquid, — at the same degree of tem- 

 perature Swedish iron of the specific gravity 7'7 (called Hoop 

 L), or 7*8 (called double bullet), just begins to crystallize, 

 forming steel, and sinking down to a specific gravity of 7*5. 



The quantity of the residuums of iron of the same descrip- 

 tion bears a very remarkable relation to the specific gravity of 

 the acid, as is evinced by the following table, showing the dif- 

 ferent quantity of residuums of 35 grains of Welsh iron from 

 the Maesteg iron-works, specific gravity 7*4'07. 



Specific gravity Residuum. Sulphuret of Lead, 

 of the acid. 



1-160 . . . 6-770 .... 1-73 



M40 . . . 9-244. .... 1*71 



1'103 . . . 13-711 .... 1-703. 



Mottled iron from the forges at Alais, departement du Gard, 

 in the south of France: 



Specific gravity of Residuum. Sulphuret of Lead, 

 the acid. 



1-16 .... 7-51 .... 606 

 Acid very much diluted 11-42 . . . . 0*6475 

 Acids still further diluted 21*49 . . . . 1*015 



Tn the fourth example I poured water over the fragments 

 of iron in a retort, the beak of which was connected with two 

 bottles of a solution of nitrate of lead, and 1 dropped only in- 

 to the retort so much hydrochloric acid as to cause a very 

 moderate evolution of hydrogen. In the last sample I put 

 only a few drops of acid into the retort, just sufficient to cause 

 a very slight attack of the iron. The third column of all the 

 samples contains the quantity of sulphuret of lead obtained. 

 The evolution of gas continued for several days, and when it 

 ceased, the addition of acid had no further visible effect*. 



* As I repeated the last experiment but one, I put some fi'agments of the 

 cast iron in the upper part of the beak of a new retort in order to witness 

 the effect of the evolving gas on iron fragments. The next day 1 found 

 the fragments converted into a black crumbly and rather unctuous mass, 

 soaked with a yellowish liquid, which fastened it to the glass. On nearer 



