the blocking means 110 through second fluid communication means 112 for bulk collection in a hopper 114 or other device by transfer through a gastight valve 116 preferably the gastight valve 116 is positioned and constructed such that high purity product passes through it without touching valve 116 operation of the above described apparatus permits preservation of the high purity solid in a controlled environment without contacting a gastight valve which could contaminate the solid and erode the valve in a preferred embodiment of the invention a noncontaminating means or means for avoiding valve wear is provided by a series of plates assembled as shown in fig1 to form a gas operated angle of repose valve 10 which may be threadably or otherwise connected to a noncontaminating silicon carbide coated graphite or silicon tube 12 from which it receives solids such as a granular product an end plate 18 of this assembly is shown in fig2 another end plate 18 also threadably or otherwise connects to a dispensing tube 14 two next to endplates 16 fig4 are oriented in the opposite directions and placed adjacent the end plates 18 in the assembly 10 two next to center plates 20 shown in fig5 are oriented opposite each other and placed adjacent each of the second plates 16 in the assembly 10 such that the openings between the adjacent plates 16 and 20 are aligned finally the center plate 22 is placed between the third plates 20 to form the serpentine flow path shown in fig1 granular product or similar solids entering tube 12 from above will accumulate somewhat in the space 24 of center plate 22 and build up in the space 26 of.