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



5416. FILTER PAPER, Whatman No. 3 (S. & S. No. 598), a very stout filter paper for general qualita- 



tive work. Slightly slower than No. 2, but very retentive. Will withstand considerable wash- 

 ing. Especially suited for fine precipitates, such as Metastannie Acid, Calcium Oxalate, and 

 Ammonium Phospho-Molybdate. Very satisfactory for filtering the solution of a fusion made 

 with Eschka's mixture in determining Sulphur in coal and coke; can also be used in recovering 

 small quantities of Silver in the form of chloride. 



Diameter, cm 7 9 11 12.5 15 18.5 



Per 100 circles $0.40 .50 .57 .74 1.04 1.48 



FILTER PAPER, Whatman No. 3, same as No. 5416, but in sheets 46.5 x 57 cm. 



5417. Per 100 sheets 10.20 



5418. Per ream (500 sheets) 46.40 



5420. FILTER PAPER, Whatman No. 4 (S. & S. No. 604), a soft paper of more open texture than the 



preceding. Extremely rapid, but not recommended for use with tlje finest precipitates. Es- 

 pecially adapted for the rapid filtration of gelatinous and large particle precipitates such as 

 Ferric Hydroxide and Aluminum Hydroxide; also useful for Pharmaceutical purposes, such as 

 the filtration of fruit juices, syrups, oils, etc. Widely used in Copper and other Ore Mining, 

 Sugar and Cement Laboratories. 



Diameter, cm 7 9 11 12.5 15 18.5 24 



Per 100 circles 30 .40 .50 .65 .90 1.30 2.22 



FILTER PAPER, Whatman No. 4 (S. & S. No. 604), same as No. 5420, but in sheets 46.5 x 57 cm. 



5421. Per 100 sheets 8.75 



5422. Per ream (500 sheets) 39.90 



5424. FILTER PAPER, Whatman No. 5 (S. & S. No. 602), a very tough, hard paper of close texture, 

 that will retain the finest precipitates, such as Barium and Lead Sulphates even when freshly 

 precipitated. Especially suited for use with solutions which are filtered with difficulty, and 

 for vacuum filtration with the Buechner funnel, etc. 



Diameter, cm 7 9 11 12.5 15 



Per 100 circles 27 .34 .41 .54 .75 



5430. FILTER PAPER, Whatman No. 30 (Dreverhoff No. 207; Munktell No. O), a single-acid washed 

 paper of low ash content, rapid and retentive. Very satisfactory for the filtration of Ammonium 

 Phospho-Molybdate, Barium Sulphate when properly precipitated, for volumetric Lime deter- 

 minations and for general quantitative work when the lowest ash is not important. Extensively 

 used in Cement and Metallurgical Laboratories. 



Diameter, cm " 7 9 11 12.5 15 18.5 



Ash weight per circle, grams .00012 .0002 .0003 .0004 .00057 .00087 



Per 100 circles .68 .90 1.20 1.50 1.90 2.70 



5432. FILTER PAPER, Whatman No. 31 (Munktell No. OB), a single-acid-washed paper, similar to 

 No. 30, but more open in texture, making it more rapid. On account of its extreme rapidity it 

 is not recommended for the finest precipitates. Suitable for the very rapid filtration of gela- 

 tinous and large particle precipitates, for volumetric determinations of Phosphates, for Silicon 

 in Iron Analysis, and general rapid quantitative separations where the lowest ash weight is 

 not essential. Extensively used in Metallurgical Laboratories. 



Diameter, cm 7 9 11 12.5 15 18.5 



Ash weight per circle, grams 00012 .0002 .0003 .0004 .00057 .00087 



Per 100 circles .68 .90 1.20 1.50 1.90 2.70 



5438. FILTER PAPER, Whatman No. 40 (S. & S. No. 589=. White Ribbon), a double-aeid-washed paper 

 of very low ash, all mineral matter having been removed by treatment with hydrochloric and 

 hydrofluoric acids. Filters rapidly and retains fine precipitates. This is the standard double- 

 washed grade for analytical purposes. Excellently suited for Barium Sulphate when properly 

 precipitated and filtered hot, also for Lead Sulphate, and for crystalline precipitates, such as 

 Magnesium-Ammonium Sulphate, etc. 



Diameter, cm 5.5 7 9 11 12.5 15 



Ash weight per circle, grams 00003 .00005 .000082 .00012 .00016 .00023 



Per 100 circles 1.10 1.20 1.70 2.00 2.30 2.70 



For Quantity Discounts, see Page 239. 



