Porcelain or high-silica crucibles or dishes are commonly used for gravimetric work. Platinum ware has advantages but is not ordinarily used, except for special determinations, because of its cost. All objects exposed to the air for anyength of time have a film of dust ad adsorbed moisture. Porcelain ware is manufactured with some of its surface unglazed; consequently, it will also absorb moisture into its interior. To use such containers for gravimetric work without proper conditioning would lead to relatively large errors in the final results. Oftentimes negative results are obtained when small quantities are involved.