104 Tropert'ies bf Steel. - %? i_y If^Ufm Ac'd. 



The Method of trying Steel. 



THE different properties belonging to each kind of ileel render the proofs of their qualitf 

 difficult even to (kilful workmen. Caft fteel will be thought of a very bad quality by him 

 who is not in the habit of working it ; as will likewife the fteel of cementation by the 

 workman who is commonly employed upon German fteel. The grain of the frafture is a 

 deceitful indication, becaufe its finenefs varies with its hardnefs ; neverthelefs good fteel 

 ought always to exhibit an even grain. Caft fteel ought to take a good polifli, and not be 

 too brittle : fteel of cementation ought to afford gravers capable of refifting percuflion with- 

 out notching or turning in the edge ; natural fteel ought to weld with eafe to iron, and 

 make good edge-tools. 



There are circumftances in which it is of advantage to afcertain whether a manufactured 

 article be formed of fteel or iron without injuring it. The means of doing this is of the 

 more confequence to us, becaufe certain unprincipled contraftors have delivered fabres with 

 blades of pure iron, to which a flight degree of rigidity had been given in the fabrication ; 

 a clrcumftance which has induced the Committee of Public Safety to publifti the dlredlions 

 we ftiall here tranfcribe, and to oblige Its agents, entrufted with the reception of every 

 kind of arms of fteel, to fubmit them to this proof. 



" If a drop of nitrous acid be placed upon the furface of polllhed iron, and, after having 

 left it two minutes, water be thrown thereon, this laft fluid will carry off the acid with all 

 Its contents, and there will remain merely a white fpot, or the colour of iron newly 

 <:leaned. 



" If the fame operation be made on a plate of poliflied fteel, the acid likewife feizes the 

 iron, but does not aft on the coaly part. This laft falls down during the folution, and 

 forms a black fpot, which the projeftion of the water does not remove, and which even re- 

 mains for a confiderable time, on account of its adhefion. 



" In order to fucceed in this operation, a diluted acid muft be ufed, becaufe the coaly 

 principle does not adhere to the furface, but In proportion to the flownefs of the folution, 

 and the weaknefs of the effervefcencc. 



" If pure or reclified nitrons acid be not at hand, the aquafortis of commerce may be 

 ufed, taking care to dilute it in a certain degree. 



" The drop of acid muft be conveyed with a ftick of glafs, or other material, which is 

 liot itfelf attacked, and cannot afford any thing capable of changing the refult. 



" The fmallcft drop fuffices. It ought rather to be fpread out, than kept together, that 

 it may mark a larger furface. The ftopper of a very fmall bottle, in which the acid is kept, 

 anfwers this purpofe very well. 



*' After having made this proof two or three times on iron and fteel compared with each 

 other, the operator will be enabled to fpeak with certainty refpedling the difference of the 

 metals." 



Artlfts have long fince availed themfelves of a method of this kind to diftinguini Damaf- 

 Cus blades. Thefe blades, as we have obfer\'ed, are compofed of the fteel and iron inti- 

 mately mixed. By this proof, fays Perret, they prefent ferpentine veins, fome of a whitifli 

 grey, others of a deep grey, and others blackifh, which are known by the name of the 



yiowers of Damafcus. 



We 



