Document dYrKJLgYxRNXkrarNNR4K0ap9

Th e Sh *w ih *Wiu s a ms Co . In t e r -Of f ic e Le t t e r Cleveland J. V. Hunn *sSv*E sc ,,ETTEB OF *eceiVED 3* i nto** Research GentePC figg. Dm Mineral Prod; Res. Lab,eci ornec A. ux..ili.aries b*Te January 31 1962 2.'CT*TED B.v Basic Lead Silicate National Lead makes basic lead silicate under U. S. 2,177,277, July 26, 19l9 The preferred method as stated in the patent specification and exampleis to precipitate lead sulfate by slowly adding sulfuric acid to a slurry of -litharge and silica. The product is filtered, washed, dried and calcined cautiously at not more than 650#G. to avoid sintering and grittimesa, The basic lead oilico chromate patent is U. S. 2,668,122, February 2, 1951* The same method is used, namely, adding chromic acid slowly to a litharge-silica slurry and then calcining at 650*C. A trace of acetic acid is usually added to the slurry. Both claims of the silico chromate patent, however, ere product claims and do net specify the method of manufacture. Three of the four basic lead silicate claims are product claims and the sols prooees olal 1* a very general one* Tarifax copies of the two patents referred to are attached. I assuffls you are aware of National Lead's "Oncar* T-l Lead Silico Titanata,_a new product which seems, to be in , the same series* . ~ , : TKtj* cot SBC TrumanRirkpetrick Mineral Products Research Laboratory N11605 06 07-SWP-000004693 \ Mr 2$, 1949. F J. WlLLIAMS/tTAL 5lf5TT! (.LEAD SUJ^CATg-^EAC SILICA} PUH*HT AWU PROCESS OF lAJWTACrt Itarch 27, 1946 2,477,277