988 THALLIUM 



squeezers or through a hole in a metal plate, to remove the alkali ; and then the warps 

 are conducted through the water cisterns, ' soured,' and washed, as before described. 



When thread or hank yarn is to be operated upon, the threads or yarns are 

 immersed in the alkali and then wrung out (as is usually done in sizing or dyeing 

 them); and afterwards they are subjected to the above-mentioned operations oi 

 washing, souring, and washing in water. 



When any fibre in the raw state, or before it is manufactured, is to be treated, it is 

 first boiled in water, and then freed from most of the water by the hydro-extractor 

 or a press ; after which it is immersed in the alkaline solution, and the excess of 

 alkali is removed by the hydro-extractor or a press ; then it is washed in water, 

 soured with dilute sulphuric acid, and washed again ; and, finally, the water is 

 removed by the hydro-extractor or a press. 



The following are the effects produced by the above operations upon cloth made of 

 vegetable fibrous material, either alone or mixed with animal fibrous material : The 

 cloth will have shrunk in length and breadth, or have become less in its external 

 dimensions, but thicker and closer ; so that by the chemical action of caustic soda or 

 caustic potash on cotton and other vegetable fabrics, an effect will bo produced 

 somewhat analogous to that which is produced on woollen by the process of fulling 

 or milling ; the cloth will likewise have acquired greater strength and firmness 

 greater force being required to break each fibre it will be found to have become 

 heavier than it was previously to being acted upon by the alkali, if in both cases 

 it be weighed at the temperature of 60 Fahr., or under. It will also have ac- 

 quired greatly augmented and improved powers of receiving colours in printing and 

 dyeing. 



THAIiZiITTM. (Symb. Tl; at. wt. 204.) The existence of a new elementary 

 substance in the deposit formed in the leaden chambers of a sulphuric-acid factory was 

 indicated by Mr. W. Crookes as far back as March 30, 1861. Mr. Crookes announced 

 his discovery in the following terms : 



'In the year 1850, upwards of 10 Ibs. of the seleniferous deposit from the sulphuric 

 acid manufactory at Tilkerode, in the Hartz Mountains, were placed at my disposal, for 

 the purpose of extracting from it the selenium, which w;is afterwards employed in an 

 investigation upon the selenocyanides. Some residues which were left in the purifi- 

 cation of the crude selenium, and which from their reactions appeared to contain 

 tellurium, were collected together and placed aside for examination at a more con- 

 venient opportunity. They remained unnoticed until the beginning of 1862, when, 

 requiring seme tellurium for experimental purposes, I attempted its extraction from 

 these residues. Knowing that the spectra of the incandescent vapours of both 

 selenium and tellurium were free from any strongly-marked line which might lead 

 to the identification of either of these elements, it was not until I had in vain tried 

 numerous chemical methods for isolating the tellurium which I supposed to be 

 present, that the method of spectrum analysis was used. A portion of the residue, 

 introduced into a blue gas-flame, gave abundant evidence of selenium ; but as tho 

 alternate light and dark bands due to this element became fainter, and I was 

 expecting the appearance of the somewhat similar but closer bands of tellurium, 

 suddenly a bright green line flashed into view and as quickly disappeared. An 

 isolated green Hue in this portion of the spectrum was new to me. I had become 

 intimately acquainted with the appearance of most of tho artificial spectra during 

 many years' investigation, and had never before met with a similar line to this ; and 

 as from the chemical processes through which this residue had passed the elements 

 which could possibly be present were limited tq a few, it became of interest to dis- 

 cover which of them occasioned this green line. After numerous experiments, I 

 have been led to the conclusion that it is caused by the presence of a new element, 

 belonging to the sulphur group ; but unfortunately the quantity of material upon 

 which I have been able to experiment has been so small, that I hesitate to assert this 

 very positively.' 



Thallium is a soft heavy metal, resembling lead ; it melts at 294 C., and is com- 

 pletely volatile below a red heat, both in the elementary state and in combination 

 (except when united with a heavy fixed metal). Prom its hydrochloric solution it is 

 readily precipitated by metallic zinc in the form of a heavy black powder insoluble 

 in the acid liquid. Ammonia added very gradually, until in slight excess, to its acid 

 solution gives no precipitate or colouration whatever, neither does the addition of 

 carbonate or oxalato of ammonia to its alkaline solution. Dry chlorine passed over 

 it at a dull red heat unites with it, forming a readily volatile chloride soluble in water. 

 Sulphuretted hydrogen passed through its hydrochloric solution precipitates it in- 

 completely, unless only a trace of free acid is present ; but in an alkaline solution an 

 immediate precipitation of a heavy black powder takes place. Fused with carbonate 

 of soda and nitre, it becomes soluble in water. 



