Page:NIOSH Manual of Analytical Methods - 7501.pdf/2

 SILICA, AMORPHOUS: METHOD 7501, Issue 3, dated 15 March 2003 - Page 2 of 8 EQUIPMENT:

REAGENTS: 1. Am orphous silica standard appropriate to the air sample, i.e., one of the following: a. fumed amorphous silica, grade CAB-OSIL® M-5, ava ilable from Cabot C orp.; www.cabot-corp.com; b. gelled amorphous silica, grade Britesorb® D300 xerogel, available from The PQ Corp., PO Box 840, Valley Forge, PA 19482-0840; www.pqcorp.com; c. diatom ace ous earth amorphous silica, grade Celite 521, available from Fisher Scientific; www.fishersci.com; d. precipitated amorphous silica, grade Zeothix® 265, available from J.M. Huber Corp.; www.hubermaterials.com. NOT E 1: Som e gelled or precipitated amorphous silicas contain up to 7% moisture. Dry all amorphous sam ples overnight at 115 °C [5]. NOT E 2: XRD signal intensity is proportional to particle size. Sieve the standards (10-µm sieve ), if necess ary, to m atc h the particle size expecte d in the samples 2. 2-Propanol, reagent grade. 3. W ater, deionized. 4. Sodium chloride, reagent grade. 5. Hydrochloric acid, 2% (v/v). Dilute 20 mL conc. H Cl to 1L with deionized water. 6. De siccant.


 * See SPECIAL PRECAUTIONS

1. Sam pler: a. Total dust: 37-mm diameter, 5.0-µm pore size, polyvinyl chloride filter (MSA, Ge lman G LA-500 0, or equiva lent) supported with backup pad in a twopiece, 37-mm cassette filter holder (preferably, conductive) held together by tape or cellulose shrink band. NOTE: Gelman VM-1 and Millipore BS filters are unaccepta ble because of high ash or am orph ous silica co nten t. b. Respirable dust: PVC filter (1.a. above) plus cyclone, 10-mm nylon or HigginsDe well (H D), w ith sam pling head holde r. Holder must keep the cassette, cyclone and coupler togethe r rigidly so that air ente rs on ly at the cyclone inlet. c. Area sample: PVC filter (1.a. above) at 3 L/min. 2. Personal sampling pumps 1 to 3 L/min (total or area); 1 .7 L/m in (nylon c yclone ) or 2.2 L/m in (HD cyclone). 3. Filters, PVC, 25-mm diameter, 0.45-µm pore size. 4. Filters, silver mem brane, 25-m m diame ter, 0.45-µm pore size, available from Sterlitech Corp., 22027 70 th Ave S, Kent, W A 980321911; www.sterlitech.com. 5. X-ray powder diffractometer with copper target X-ray tube and scintillation detector. 6. Glue or tape for securing Ag filters to XRD holders. 7. Reference specimen (m ica, Arkansas stone or oth er sta ble sta nda rd) for data normalization. 8. Low temperature plasma asher (LTA) or muffle furnace. 9. Filtration apparatus with side-arm vacuum flask and 25- and 37-mm filter holders. 10. Sieve, 10-µm pore size, for wet sieving. 11. Furnace capable of maintaining 1100 °C for 6 h or 1500 °C for 2 h and of tem perature programm ing to 500 °C at 50 °C/min. 12. Crucibles, platinum, with covers. 13. Analytical balance (0.01 m g). 14. Stirrer, magnetic, with thermally-insulated top. 15. Ultrasonic bath or probe. 16. Pipets, 2-to 25-mL.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition