In lab...last one ...where I had to go and heat these brass cartileges (I really don't think that's spelled correctly) and the oven was off. So my substitute lab tech for the day went and ...created a oven...yep you hear me right created a oven of sorts...I was curious as to know whether this is alright in practice or technically it shouldn't be done.
This was done by placing the 2 brass cartileges into a uncovered weighing bottle. Then that was placed directly onto a hot plate. After this a large beaker was placed over the weighing bottle. Then it was heated for a period. I was then asked after awhile if it was dry...I replied that I really didn't know when it was technically dry since ...I didn't know if 30 min in the oven equated to 30 min on a...hotplate??
Not only do I think this to be faulty to some degree..wouldn't it go and eventually crack the glass if the beaker and weighing glass were directly heated?
#2. After washing the brass cartileges with alconox and heating them they were placed into my dessicator. The next day they weren't a golden color anymore but rather were completely silver. I would guess that oxidation occured but if so why didn't this occur before they were washed as they were originally stored in weighing bottles which were placed in a dessicator?
The answer to the first one is, maybe. It all depends upon the temperature of the hot plate. Give the lab tech an A for ingenuity, anyway. If the top of the hot plate was hotter than 100 C the brass should be dry after 30 minutes. You wouldn't want the hot plate to be too hot since it might oxidize the surface of the metal. As to breakage, some of the older pieces of glass made of KIMAX were less stable to temperature shock and broke rather easily. I don't see much KIMAX glassware anymore and I suspect the glassware you used was made of pyrex. Pyrex is more stable to thermal shock. It will break sometimes. It isn't good practice to place a DRY pyrex container on a HOT hot plate surface; however, your samples were solid and even if the glassware broke the samples would not be lost. As to question 2, I don't know the answer.
By the way, there is another kind of glassware. It's made of VYCOR. A piece of that can be heated red hot over a flame, then doused in ice cold water, and it will not break. A fellow student in graduate school claims to have broken a piece of Vycor glass that way but we always thought he was making up a story.
I thought that was clever too.
I really don't know the hotplate temperature since he set it..
Speaking of glassware, there was this incident where another student went and heated water (about 1600ml) in a 2000ml beaker. After heating for about 15 min if I can estimate since I wasn't paying attention the glass cracked and allowed the water to get all over the hotplate. It caused alot of commotion since it as you would expect sizzled and made alot of noise. Maybe it was unstable?
Then again about the glassware material..my school's "equipment" is technically so old that I wouldn't be surprised if I found KIMAX glassware there...I was told by a classmate in my lab section that our lab...was extremely inadequate and old compared to her school which she actually goes to during the year upstate.
With VYCOR, which I assume is expensive..Why do you say a "piece" of that glassware can be heated..Is it used for normal say volumetric flasks and beakers and such or is it specially used for .."pieces"
In addition, what is Vycor glass used for?
Here is a link to Vycor. The piece I was talking about was about 1 foot square and was used for the demonstration I mentioned. The beakers etc I have seen made from Vycor are thicker than the usual pyrex glassware AND they have areas that are uneven in thickness. I don't know if that part of the manufacturing process has been improved or not. I'm surprised that a Pyrex beaker of boiling water broke unless the beaker had a crack in it initially. That's the usual case.
Sorry. I omitted the link. Here it is. http://en.wikipedia.org/wiki/Vycor
So vycor is actually made by one company.
I don't really want to go and pry but if it isn't too much of a bother..may I ask why that person went heated a 1 foot square of Vycor?
This isn't related to the glassware but to the bleaching agents in tooth whitening products I found a interesting journal from the British Dental Journal...I'll post that when I go and list the ingredients which I still have to look up but when I try to post a link I can't and I'm not exactly going to copy the whole journal and post that. I asked last time how to post a link and well it went unanswered...
I just tried it and I still can't just copy and past a link..
I would appreciate it if you helped me out with that.
Thanks Dr.Bob =)
I THINK, but I'm not sure, that it takes special permission to have the capability to post a link and I THINK, only some of the volunteers have that capability. I know I can do it but I could not when I first started helping on this board. For the Vycor, the 1 foot square plate of Vycor was heated red hot and plunged into ice water to demonstrate to a class of freshmen students (about 400 or so ion each class) the difference between ragular glass, borosilicate glass (pyrex) and Vycor. The prof said he had been using that same piece of Vycor for over 10 years and it hadn't shattered in that length of time. And he demonstrated it to three or four classes. So I suppose it was "mistreated" that way probably a dozen times a year and it still was in one piece after several years.
=( Alright then.. I highly doubt that I would EVER get the permission to go and post anything here... I guess I'll just summerize what I find later ...just another note is that I won't be posting it on the old post but rather a new one.
Well that is a large class...I basically had just 40 or so people in my class in gen chem and there were 4 sections...In analytical chem this summer all the people in the 2 sections totaled about 20 people. I would say that it would eventually break from such abuse but if it isn't supposed to break... But whatever I'm blabbering now so just ignore me =D
It sounds like your lab setup has some outdated and potentially inadequate equipment. It is not ideal to create an oven-like setup using a hot plate and glassware without proper precautions. The temperature control may not be accurate, and there is a risk of glass breakage if the glassware is not suitable for direct heating.
Regarding the change in color of the brass cartilages, it is possible that oxidation occurred during the washing process. Oxidation can cause the surface of the brass to change from golden to silver. However, it is unclear why the oxidation did not occur before washing if the cartilages were stored in weighing bottles in a desiccator.
As for Vycor glass, it is a specialized type of glassware known for its thermal resistance. It is often used for scientific applications where high temperatures and harsh conditions are involved. Vycor glass is more expensive and not commonly found in standard laboratory setups. It is typically used for specific experiments or demonstrations that require its unique properties.
Unfortunately, I am not able to assist with posting links as it requires special permission on the platform. If you have any more questions or need further assistance, feel free to ask.