{"id":2868,"date":"2016-06-20T10:15:48","date_gmt":"2016-06-20T14:15:48","guid":{"rendered":"http:\/\/www.ttgnet.com\/journal\/?p=2868"},"modified":"2016-06-20T10:15:48","modified_gmt":"2016-06-20T14:15:48","slug":"monday-20-june-2016","status":"publish","type":"post","link":"https:\/\/www.ttgnet.com\/journal\/2016\/06\/20\/monday-20-june-2016\/","title":{"rendered":"Monday, 20 June 2016"},"content":{"rendered":"

10:15 –<\/span> Barbara is off to the gym and running errands. This afternoon and the rest of this week we’ll be filling and labeling bottles and making up science kit subassemblies.
\n<\/span><\/p>\n

One of the problematic chemicals has always been starch indicator, which is a suspension of “soluble” starch in water. We use a 10% m\/v solution of thymol in IPA as a preservative. That generally works pretty well, but we sometimes get mold or fungal growth in some of the bottles. We just threw out a bunch of them the other day that had assumed a dark brownish gray cast. They’d still serve their intended purpose, detecting very small amounts of iodine, but their ugliness offended me. So yesterday we tried something different. I made up a small batch of the starch indicator, enough to fill 60 bottles. After they were filled and capped, we put them in a pot of boiling water and let them boil for ten minutes or so. That’s enough to kill any microorganisms present, although not spores.
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The bottles are polyethylene, which softens but does not melt at the temperature of boiling water. I was a bit concerned that boiling would deform the bottles severely, so we ran a test recently with just one bottle in a pan of boiling water. It swelled a bit, but did not melt or deform.
\n<\/span><\/p>\n

Killing spores would require heating the bottles to 121C (250F) in a pressure cooker or autoclave. Unfortunately, it would also melt the bottles. So if just boiling them doesn’t keep them from growing mold\/fungus, we’ll have to use a 19th century technology which is still occasionally used today for special purposes. It’s called Tyndallization<\/a>, and was widely used for preserving food before pressure cookers became widely available.
\n<\/span><\/p>\n

\n","protected":false},"excerpt":{"rendered":"

10:15 – Barbara is off to the gym and running errands. This afternoon and the rest of this week we’ll be filling and labeling bottles and making up science kit subassemblies.\n<\/p>\n

One of the problematic chemicals has always been starch indicator, which is a suspension of “soluble” starch in water. We use a 10% m\/v solution of thymol in IPA as a preservative. That generally works pretty well, but we sometimes get mold or fungal growth in some of the bottles.<\/p>\n

 » Read more about: Monday, 20 June 2016  »<\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[11],"tags":[],"class_list":["post-2868","post","type-post","status-publish","format-standard","hentry","category-science-kits"],"_links":{"self":[{"href":"https:\/\/www.ttgnet.com\/journal\/wp-json\/wp\/v2\/posts\/2868","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.ttgnet.com\/journal\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.ttgnet.com\/journal\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.ttgnet.com\/journal\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.ttgnet.com\/journal\/wp-json\/wp\/v2\/comments?post=2868"}],"version-history":[{"count":0,"href":"https:\/\/www.ttgnet.com\/journal\/wp-json\/wp\/v2\/posts\/2868\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.ttgnet.com\/journal\/wp-json\/wp\/v2\/media?parent=2868"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ttgnet.com\/journal\/wp-json\/wp\/v2\/categories?post=2868"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ttgnet.com\/journal\/wp-json\/wp\/v2\/tags?post=2868"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}