1、BsI N*E!2 49 E lb24669 0079298 9 u, 22, October, 1949 1 Nom.-The Ittsttt4tiott desires to call attentiort to the fact that this standard is intended to include the techitical $rouisions necessary for the sr . IC i* Additional clauses * -_ Is of the metal container? in Appendix F. k The material shal
2、 st of hydrated silica in the gel form. It shall be I l uniform in character, and suitable for use as a drying agent for air. . 2. State of division. : The whole of the material, when tested by the method described in Appendix A, shall pass through a sieve o which the aperture is one quarter of an i
3、nch, and not less than 95 ,per cent by weight of the material shall remain on b, No. 30 B.S. sieve.“ 3. Moisture. The loss in weight of the material on ignition shall not exceed 7 per cent. - 4, Drying efficiency. The material when tested by the method described in Appendix B, shall have a drying ef
4、ficiency of not less than 98 per cent. 6. Drying capacity. a drying capacity of not less than 45 per cent. 6. Sulphate content. When tested by the method described in Appendix D the total sulphate content of the material, Calculated as sodium sulphate (Na2 SO,), shall not exceed 4.0 per cent and the
5、 free acidity, calculated as sodium sulphate (Na, SO,), shall not exceed 1 5 per cent. e The material, when tested by the method described in Appendix C, shall have 7. Packaging. The containers shall comply with the requirements giuen in Appendix F. 8. Storage of sample. with an efficient stopper or
6、 bung. is drawn shall then be closed securely. The material shall be packed jn 1 lb. or 16 lb. metal containers as specified. When sampling silica gel, the sample shall be placed in a dry bottle fitted The drum or container from which the sample d) B.S. 410. Test sieves I. 1 , 92, October, 1949 .2 A
7、PPENDIX A. Method for the Determination of State of Division. 100 g. of the sample shall be placed on the specified sieves and shaken by hand for a maximum time of 2 minutes. APPENDIX B. Method for the Determination of Dvying Efflciency. A suitable apparatus for carrying out this test is shown in Fi
8、g. 1. Air is drawn by suction through a series of 8 vessels A to H at the rate of 25 litres per hour, measured by a suitable flow- meter attached to the tube H. The air is humidified by passing through the vessel A, consisting of a set of Mohr potash bulbs containing water, maintained at 30 C. in a
9、water-bath. Vessels B, C, D, E, and F are maintained at 20 C, in a second water-bath. Vessels B and C are two sets of Liebig potash bulbs containing water for saturating the air with moisture at 20 C., and D and E are air-traps to remove entrained water droplets, D being a set of Mohr potash .bulbs
10、and E a small bottle fitted with a thermometer. E is filled to two-thirds of its volume with a mixture of in, glass balls and 34 in. glass tubes to help in the removal of entrained water The connections between vessels B, C, D and E and the cork of E carrying the thermometer, are arranged to be belo
11、w the surface of the water in the 20C. bath. . The three tubes F, G and H are U-tubes, each with a single absorption limb with stopper having an internal diameter of 1 * 4 cm., and length of 14 5 cm, below the stopper. Tube F in the water- bath carries the silica gel imder test, while G and H are fi
12、lled with phosphorus pentoxide mixed with glass beads, n c O E Water bath at 20C I : C ?i FIG. 1. Apparatus for the Determination of Drying Efficiency. To carry out the test, 10 g. of the freshly regenerated silica gel shall Se placed in tube F and air drawn through the apparatus for 3 hours. The fl
13、ow of air shall then be stopped and tubes I?, G and H removed, dried, and separately weighed. The tubes shall then be re-attached to the apparatus, and after an interval of 15 minutes to allow tube F to regain the temperature of the bath, the flow of air shall be recommenced. The flow of air shall b
14、e continued for 30 minutes at the rate of 25 litres of free air per hour, at the end of which time the flow shall be stopped and the tubes again removed, dried, and weighed. After the test the tube H shall not differ in weight by more than one milligram. The gain of weight (Y!) ef tiibe F shall be t
15、aken as the moisture absorption of the silica gel, and the sum of the gains in weight (W4-w) of tubes F and G shall be talten as the total moisture content of the 12.5 litres of air passing in the 30 minutes test. The drying efficiency of the silica gel shall be taken as the moisture absorption of t
16、he silica gel expressed as a percentage of the total moisture content of the 13.5 litres of air passed, Le. w x 100 Wt-w Drying efficiency = BSI M*Z2 49 1624669 0899300 3 -. . 3 APPENDIX Cm Method for the Determination of Dvying Capacity. A weighed crucible containing 5 g. of freshly regenerated sil
17、ica gel shall be exposed, open, over a saturated solution of disodium hydrogen phosphate in a desiccator for 5 days at a temperature of 2loC., and then re-weighed. The gain in weight expressed as a percentage of the original weight of the silica gel shall be taken as the drying capacity. APENDIX D.
18、Method for the Determination of Souble -Sulphates. .- .- - I- - . . *. 10 g. of the material shall be powdered and 100 ml, of boiling illed water poured on to it, the whole being heated in a covered vessel on a boiling-water bath for two hours, after which it must be cooled, with suitable precaution
19、s against contamination by atmospheric impurities. The solution shall then be filtered through a dry sintered glass filter, and the gel waslied with a further 10 ml. of boiling distilled water. The filtrate shall be titrated with a standard solution of NI1 caustic soda of analytical reagent quality,
20、 using methyl orange as indicator. This gives the free Thk titrated solution shall then be maGe acidic with a few drops of hydrochloric acid and brought to the boil. Sufficient 10 per cent solution of barium chloride shall be taken to precipitate all the suiphates present, heated to boiling point an
21、d added gradually to the boiling fi!trate. . The precipitate shall then be filtered on to a No. 42 Whatman filter paper, and washed free from chlorides with boiling distilled water. The-mashed precipitate and the paper shall be placed in a tared crucible, and heated very slowly over a bunsen burner
22、until the paper is totally charred. The flame shall be increased, and the heating continued until all the carbon hasdisappeared and no further loss in weight can be detected. - - acidity. .- - .- Then : * = per cent sulphates as sodium sulphate Weight X 142 X 100 233 X 10 ml. NI1 NaOH X 0.071 X 100
23、10 per cent sulphuric acid as Na,S04. APPENDIX E. Regeneration. The absorbed moisture can be removed by heating to a moderate temperature (250O C.) and this The gel after regeneration will still retain about +per cent restores the absorptive power of the gel. of moisture but this is probably combine
24、d and its removal would affect the capacity adversely. APPENDIX Fm Details of tttetccl contaiilers. with the following requirements :- The metal containers used for packaging of silica gel shall comply 1-Zb, titts. lever ring with soldered side seams. an airtight closure. The tins shall be of the le
25、ver lid type with tagger plate seamed in under the After filling, the base of the tin shall be spun on, forming The tins shall conipIy with the following particulars :- Shape - Cylindrical. Dimensions - Approx. 4 in, diameter X 4% in. deep. Quality and gauge of metal used - Tinplate 95 lb. substance
26、. Amount of ullage allowed - Approx, 5 per cent. Method of sealing - Lever lid with tagger plate, soldered side seam, spun on solutioned bottom, 1 H, 22, October, 1949 4 APPENDIX F.-(Colztilzued). 16-1b, metal colttainers. in cases, . I Shape . . . -. Rectangular. . The containers shall be of a patt
27、ern suitable for packing for transit The containers shall comply with the following particulars :- I .I .- Dimensions - -9% in. X 6 in. X 12% in. Quality and gauge of metal used - (SWG) Body - Tin plate 108 lb. substance Top and bottom - “ -.-.I . 99 $9 1 x I - Approx. 5 per cent. L- - Amount of ull
28、age allowed Method of sealing All seams shall be soldered and the lever lid I -spot soldered. , .- .- This specification having been approved by the Aircraft Industry Standards Committee and endorsed by the Chairuan of the Engineering Divisional Council, was published under .the .authority of the Ge
29、neral Council of the Institution as a British Standard on 17th October, 1949. - . ., r. .II. I. NOTE, .; . .- In order to keefi abreast of progress in the indatstries concerned, British Standards are subject to periodical review. Suggestions for imbroveinents will be recorded and in dire course brou
30、ght to the notice of the committees charged with the revision of the Standards to which they refer. British Standards are revised, when necessary, by the issue either of ameirdment slips or of revised editorts, It is important that users of British Sttcndards sttoadd ascertain thnt they are itt possession of the latest nmendwzerzts or edition. .
