Document 99Y2wnmVadY66bD3qOEeJNb6L

N A TIO N A L LEAD COM PAN Y STAN D ARD M ETH OD O F TEST N o. X 135- 57-____ Ma t e r i a l Pigment Mixtures D e t e r m i n a t i o n s I d e n t ific a t io n of M-50 Figment by means of th e Microscope Purpose Th is method i s to id e n t ify M-50 in mixed pigment p ain t system s, p a r t ic u la r ly t o d iffe r e n t ia t e M-50 p a r t ic le s from th ose of r ed lead , le ad chromate and ir on oxide. Apparatus and A cessor ies Microscope, p o lar iz in g equipped to give 600-700X. A bin ocu lar stan d i s p r e fe r r e d . O b ject ives: iiOX and 60X dry. Eyepieces: 15X. Eyepiece micrometer d isc , American O pt ical Company #llt09. 10 mm square r u led in t o 0.5 mm sq u ar es. Substage condenser with diaphragm, 1.25 - l.liO N.A. Microscope lamp. Bausch & Lomb Research Microscope Illu m in at or 31-33-35-11, 6 Volts 108 W atts ribbon filam en t prefocu s base lamp; tran sform er fo r 115 Volts 60 cycle A.C. Microscope sl id e s 50 x 75 mm Fish e r Catalogue 12-550. Micro cover g l a sse s: 19 x 19 mm #1 Fish e r Catalogue 12-52lu Sp at u la and len s paper . Mounting Mediae: a) Acr y lic Resin Solu t ion - Acryloid F-10 manufactured by The Resin ous Products and Chemical Company, P h ilad elp h ia, P a. Mix 35 ml of Acr yloid F- 10- solu t ion w ith 65 ml of Xylol and keep in a w ell stoppered dropping b o t t le . b) Xylol. c) Sh illa b e r 's Immersion O il, low v isc o sit y . .. N19649 0018412 N ATI ON AL LEAD COM PAN Y M ETH OD N o. 0.3 Normal Hydroch loric Acid sat u r at e d w ith hydrogen su lfid e . 1:1 Hydrochloric Acid w ith d ist ille d w ater. Con^cen trated solu tion of ammonium ace t at e ' in d istilled w at er. Procedure . St ain in g Technique .. P lace a sm all amount of pigment on a clean microscope slid e , and add t o i t a drop o f ac r y lic r e sin so lu t io n . Usin g a fin ge r , in cor por ate th e pigment in t o the r e sin so lu t io n and spr ead i t out on the slid e in t o a t h in uniform film . Th is act ion must be f a s t and the fin ge r withdrawn from th e slid e befor e th e film se t s, t o avoid ob ject ion able st r e ak in g. Allow th e xy lo l t o be com pletely evaporated from the film . Th is can be ach ieved by blowing a b la st of h ot a i r from a h air d r ie r over th e pr ep ar at ion or h oldin g th e slid e over a hot p la t e . When the film i s dry, place a drop of 0.3 normal h ydroch loric acid sat u r at ed w ith hydrogen su lfid e on th e slid e and cover w ith a cover g l a ss. Next t o i t , p lace a drop of Sh illa b e r 's o i l and cover w ith a cover g la ss. The o i l i s u sed as a blan k. Place th e slid e on th e microscope st age and f i r s t observe the hydrogen su lfid e p r ep ar at ion . P ain t s, in most case s, may be mounted in a sim ilar fash ion by p lacin g a sm all drop of th e w ell mixed p ain t and follow in g the exact procedure described above. Appearance o f M-^O P a r t ic le s St ain ed w ith Hydrogen Su lfid e - The p a r t ic le s of th e M=50 pigment ar e e a sily recogn ized as th ey r ap id ly assume a brownish b lack co lo r . The o r igin al orange co lor im parts a warm tone of b u ff or beige in th e f i r s t st age s of th e r eact io n w ith hydrogen su lfid e . In a m ixtu re, follow in g t h is procedu re, on ly th e p a r t ic le s o f M-50 pigm en t w ould s t a i n . Fr ee s i l i c a p a r t i c l e s w ould st a n d ou t K& TiQ N AL LEAD COM PAN Y M ETHOD HO. t 135-57 3-PAOEE---- -- as co lo r le ss e n t i t ie s. The red le ad does n ot st a in . The ir on oxide does n ot appear t o change co lor . Basic le ad chromate w ill change to. so lid b lack . However, i t s p a r t ic le ch ar act er and p o lar izin g q u a lit ie s would d ist in gu ish i t frpm M-50 p a r t ic l e s. Removal of M-50 Coatin g . A qu an tity o f M-50 pigment i s t r e at e d in a beaker with 1:1 h ydroch loric ac id . I t i s b e st t o b r in g th e mixture t o a b o il and continue b o ilin g fo r about 15 m in utes. The pr ep ar at ion i s allowed t p cool, se t t le and i s decantedo Aft er fiv e d ecan t at ion s, most of th e h ydroch loric acid and ch lor id es are removed. The sediment i s t r e a t e d with con cen trated ammonium ace t at e and i s b o ile d fo r about 5 - 1 0 m in utes. The pr ep ar at ion may be fi lt e r e d or washed by decan tation w ith hot d i st i l l e d w at er . The r esid u e i s s i l i c a from which th e act ive coatin g was removed. See at tach ed ph otograph s. To v e r ify t h i s, mount a sm all- p or t ion of th e dry r esidu e in ac r y lic r e sin and st a in w ith 0.3 normal h ydroch loric acid sat u r at ed w ith hydrogen su lfid e , as d escr ib ed above under "St ain in g" . Under th ese con d it ion s, th e p a r t ic le s o f fr e e s i l i c a w ill remain p e r fe c t ly c le ar and c o lo r le ss. They do n ot st a in . D ist in gu ish in g of M~50 P a r t ic le s in Mixtures by Means of th e Microscope With Br igh t f i e l d illu m in at ion , Dry powders or mixed p ain t system s in which M-50 pigment i s one of th e in gr e d ie n t s, can be b e st st u d ied under th e microscope when mounted in a c r y lic r e sin . The M-50 p a r t ic le s have the shape of ground s i l i c a . The average p a r t ic le siz e o f a t y p ic a l M-50 pigment i s about 8.0 m icron s. The p a r t ic le s are t r an slu cen t , have Si'ft 'HCj MAL, L E A D C O M P A N Y METHOD NO. a yellow ish to orange color and are an gu lar in ch ar act er . The p a r t ic le s o f r ed le ad , ir on oxide and b a sic le ad chromate vary accordin g t o th e type m at er ial u sed , however, none of them would have th e shape of M-5o pigment. D ist in ct io n of M-gO P a r t ic le s by Means of the P olar izin g Microscope The same slid e which was used t o study a m ixture under th e b r igh t fi e l d m icroscope, can be used fo r th e p o lar iz in g m icroscope. The p a r t ic le s ar e brough t in t o sh arp fo cu s, and the n ico l prism s cr o ssed . The st age i s r o t at e d and any changes t h at might take p lace in th e ch ar act er of th e p a r t ic le s n oted. Under th ese con d it ion s, th e p a r t ic le s o f M-50 pigment remain dark; the p a r t ic le s of red le ad would e xt in ct i n one p o sit io n and assume an in ten se green color a t p o sit io n s 90 from t h at of e xt in ct io n ; th e b asic le ad chromate would alt e r n a t e ly assume an oran ge-red color ; and, the iron oxide emits alt e r n at e ly a yellow ish color while the un coated s i l i c a p a r t ic le s w ill assume a lt e r n a t e ly a p ale white color0 0018415 -M A T iQ W AL , L E A P C O M P A N Y XJ2MIMETHOD NO 4* AO PHOTOMICROGRAPHS l COLOR AT 1200X Basic Lead Si l i c e Chromate M-50 Pigment M-50 Pigment A ft er Treatment With Hydroch loric Acid and Ammonium Acetate* Si l ic a P ar t ic le s are St r ip p ed of Active M ater ial* NATI ONAL. LEAD CO M PAN Y P RO P U CT SP ECIFICATIO N N o. P l o g 58a . PROD UCT M-gO Pigment (Basic Lead Si l ic a t e - Chromate1) P RO P ERTIES M IN . I MAX. METHOD O F Chromium t r io x id e , CrO^, % Coarse p a r t ic le s (+325 mesh), % Ign ition lo ss, % Lead monoxide, PbO, % \ O il ab sor pt ion , g per 100 g S i l i c a , Si02, % 5.10 U6.2 10 L5 .5 5.60 0.10 0.20 U8.7 18 i+8.5 X 131 X 112 X 117 X 175 X ill X 127 KF 0018417 Date Issued October 20, 1958_____________