[ 207 ] 



XXII. On the Production of a Columnar Structure in Metallic 

 Tin. By Dr. T. Fritzsche of St. Petersburg*. 



THE occurrence of a curious structural change in block tin 

 from Banca was observed by Dr. Fritzsche. The metal 

 became crystalline, and fell into small pieces having a columnar 

 form. This change was attributed to the intense cold prevailing 

 in St. Petersburg at the commencement of the year 1868. 



Dr. Fritzsche thus describes the experiments instituted to 

 confirm his view: — "Although I was persuaded that this phe- 

 nomenon was produced by the intense cold that we had at the 

 beginning of 1868, I wished to prove it by experiments. These 

 experiments I have lately completed. I exposed some fragments 

 cut from a block of Banca tin in an alcohol-bath reduced to the 

 temperature of — 32°-35° R. They underwent a change exactly 

 similar to that in the blocks in question. 



K It is necessary for a like cold to be sustained for some hours 

 to induce the commencement of the crystallization, which showed 

 itself by the appearance of button -like prominences of a steel-grey 

 colour rising from the surface of the tin. Each prominence re- 

 presents a centre from which the crystallization proceeds, if the 

 cold be sustained. Gradually the meeting of the acicular crys- 

 tals produces fissures at the points of contact, and the fragment, 

 the volume of which is much augmented, falls in pieces, which 

 are very friable and crumble between the fingers. 



"A remarkable fact is that elevation of temperature causes 

 the steel-grey colour to disappear. This may be shown by 

 plunging the steel-grey tin (enclosed in a sealed glass tube) into 

 hot water, when the natural white colour reappears but without 

 the former metallic lustre. This change of colour is not attended 

 by a loss of weight ; neither is the transition of cast tin into 

 the crystalline modification, in the presence of air or in alcohol, 

 attended with any loss of weight. I have met with cavities in the 

 altered blocks, one of which had a capacity of -80 cub. centim.; 

 I do not believe that such large cavities were formed during the 

 cooling of the blocks. I attribute their formation to the act of 

 crystallization ; but on cutting these blocks I found that the 

 change was only superficial, the centre being in the natural con- 

 dition. I have there found similar cavities ; and it is beyond 

 doubt that they existed before the commencement of the change. 

 As yet English tin has resisted the crystallization ; but Banca tin 

 also undergoes the change even after being melted. 



" I shall continue my researches, as it is necessary to compare 

 specific weights and to make analyses. I will communicate the 

 ultimate results if they are of sufficient importance/" 



* From a letter to Mr. Graham, dated June 18, 1869. Communicated 

 by Mr. Graham. 



