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BAIRD &TATLOCK (LONDON) LTD. 



i 2662* White Ribbon. 589. 



Most saleable kind. Prices same as No. 2661. 



The filtering speed of the white ribbon brand and its capacity to retain deposits is such as appears to be requisite for most 

 i analytical purposes. We therefore always deliver this brand unless otherwise ordered. 



The filters made out of this material filter quickly and retain a properly treated deposit of BaSO 4 . 



2663* Blue Ribbon. 589. 



Price same as No. 2661. 



This brand blue ribbon is made from close, firm material. Consequently these filters must not be expected to work 

 quickly, for which reason it is best to use them when an air-pump is employed, or if possible, as folded filters. 



They are suitable for the finest precipitations or opaqueness which is not kept back by the brands black ribbon or white 



libbon. 





2664* Yellow Ribbon. 589. 



The filters of this brand are identical with white ribbon quality. But after being freed from mineral con- 

 stituents, they are also scoured with ether. 



2665* Filters washed with HC1 and HF1. Schleicher & Schull's, 590. 



These niters, which are also treated with HC1 and HF1, are thinner than the brands specified under No. 589. 

 They therefore contain slightly less ash and filter slower than No. 589, white ribbon, but otherwise well retain 

 fine precipitates. 



In consequence of the treatment with HC1 and HF1, any soluble mineral matter is extracted from these filters, which probably 

 represent the purest form of cellulose. That the mineral constituents cannot be entirely removed is confirmed by our numerous 

 experiments, and particularly also, by those made by Mr. W. Lange (Reports of the German Chemical Society of the year 1878, 

 P- 323 " The Nature of the Silicides found in Plants "). He also treated linden-bast successively with HC1, KHO, and boiling 

 alcohol. Cellulose thus treated and purified he dissolved in ammonic oxide of copper ; he then filtered and precipitated with 

 HC1, and several times repeated this process of dissolving, filtering, and precipitating. Notwithstanding this exhaustive process, 

 the ashes proved not to be free of SiO ? , CaO, and Fe.,0.,. Nearly half of the ashes consisted of SiO,, such as we have also found 

 to be the case when making our experiments, and which is confirmed by the periodical control of our chemist. 



Mr. Fresenius (Zeitschrift fur analyt Chemie, 1883, p. 241) has also examined these filters treated with HC1 and HF1, and points 

 out that the weight of the filter-ash of this make is so small that it need not be considered even in exact analyses 



2666* Filter Paper Clippings, of 589 chemically pure paper 



perlb. 016 



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|C EMICAL AND SCIENTIFIC APPARATUS AND PURE CHEMICALS. 



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