CENTRAL SCIENTIFIC CO., CHICAGO, U. 8. A. 241 



No. 5460. No. 5462. 



5440. PILTER PAPER, Whatman No. 41 (S. & S. No. 589', Black Ribbon), a double-acid-washed paper 

 similar to No. 40, but more open in texture and therefore filters more rapidly. Suitable for 

 Iron, Aluminum, and other gelatinous precipitates which can be filtered quickly and washed 

 rapidly and easily. Widely used in determining Silicon in Iron and Steel Analysis. 



Diameter, cm 7 9 11 12.5 15 



Ash weight per circle, grams 00005 .000082 .00012 .00016 .00023 



Per 100 circles $1.20 1.70 2.00 2.30 2.70 



5442. FILTER PAPER, Whatman No. 42 (S. & S. No. 5893, Blue Ribbon), a double-acid-washed paper, 

 similar to No. 40, but much harder and extremely close in texture. On account of its close 

 texture it is recommended for use with the filter pump and as folded filters where possible. 

 Especially adapted for the finest precipitates which tend to pass through the filter paper, such 

 as Barium Sulphate when precipitated in cold solution, and in general for precise analytical 

 work where speed is not important. 



Diameter, cm 5.5 7 9 11 12.5 15 



Per 100 circles 1.10 1.20 1.70 2.00 2.30 2.70 



5444. FILTER PAPER, Whatman No. 43 (S. & S. No. 589', Yellow Ribbon) a double-aeid-washed paper, 

 of the same stock as No. 40, but having been subjected to an additional chemical process which 

 renders it fat-free. Especially suited for the recovery of the ether extract in the Roese-Gottlieb 

 Fat Test, and in general for any purposes requiring a fat-free paper. 



Diameter, cm 9 11 12.5 



Per 100 circles 2.20 2.55 2.80 



5446. FILTER PAPER, Whatman No. 44 (S. & S. No. 590), a double-acid-washed paper of thinner sub- 

 stance and lower ash content than the preceding numbers. It will retain the finest precipi- 

 tates, but is slightly slower in filtration than No. 40. No. 44 is recommended for use when the 

 greatest possible degree of accuracy in quantitative work is required. 



Diameter, em 7 9 11 12.5 15 



Ash weight per circle, grams 00003 .00005 .000077 .0001 .00014 



Per 100 circles 1.50 2.20 2.55 2.80 3.60 



5452. FILTER PAPER, Whatman No. 50 (S. & S. No. 575), a paper specially hardened by treatment 

 with Nitric Acid. Very tough, will resist great pressure, and retain the very finest precipitates. 

 Can be used repeatedly, the hard smooth surface permitting precipitates to be scraped or 

 washed off without injury to the paper. Especially recommended for use with vacuum. Suit- 

 able for very fine precipitates and for filtering corrosive liquids such as Acids and strong 

 Alkalies. Should be used when it is desired to transfer a precipitate without ignition. Wide- 

 ly used for filtering Biological products, as the hardened surface prevents contamination of 

 the filtered product by particles of paper when scraped off. Can be used as a substitute for 

 platinum cones, and as supports for large folded filters to prevent them bursting at the points. 



Diameter, cm 5.5 7 9 11 12.5 15 18.5 24 27 



Per 100 circles 90 1.20 1.70 2.00 2.30 2.70 3.60 6.10 7.30 



For Quantity Discounts, see Page 239. 



5460. FILTER PAPER BOXES, of cardboard, square, telescoping form, to hold 100 filters. Very con- 

 venient for keeping filters clean and free from dust. 



No A B C D 



For filters, cm 9 11 12.5 ]5 



Per dozen 30 .45 .55 .60 



5462. FILTER PAPER CASE, of japanned tin, convenient for holding filters of different sizes. Will 

 take 6 sizes from 7.5 cm to 18.5 cm in diameter 



