Heat Heart (ヒート ハート Hīto Hāto) is the fifty-seventh chapter of the Dr. Stone manga.
Summary
Suika tries out the telescope and is impressed with how far she can see. Senku warns her not to stare at the sun through the telescope as soon the sun will rise.
Outside Chrome's shed, Kohaku is watching the basket full of the alleged Scheelite ore they mined expecting the mineral to sparkle with the first rays of dawn. People are impressed, and Senku is very satisfied when this finally happens. Ruri mentions that it's like a pile of jewels, then Senku adds that it literally is, besides being a treasure containing their very rare metal.
Not everyone is as enthusiastic, Magma complains that to him they are just heavy rocks they made him dig out, Gen correcting that those rocks will lead to their victory in the war against Tsukasa. Kokuyo then steps in, misconstruing this remark as a suggestion that the rocks will be used as projectiles, as rocks that heavy sure would do some damage. Kohaku calls him out for being stuck in the stone age.
Gen proceeds to explain everyone that Tsukasa's army can't be beat by force, so they'll use the mineral to make telephones and outsmart them with information warfare. At the heart of the cellphone is the tungsten metal contained in the jewels, Senku says.
He is asked by Kohaku about how to get the metal out of the jewels, he replies that it is very hard. This exchange has not even finished before Mantle and Magma have jumped to action and started smashing the rocks, much to the shock of everyone, but he is soon validated when it's pointed out that they needed to pulverize them anyway, though Magma didn't know that.
Kokuyo makes an observation about how rare it is to see Magma helping out of his own volition, asking Senku if something happened in the cave. Senku prefers not to tell and states nothing comes to mind.
So the process to craft the tungsten filament begins. The simplified explanation that Senku gives is that he'll turn the powdered jewels into something similar to toothpaste, and heat it up in a glass container filled with hydrogen at a very high temperature, at least 1000 degrees celcius, so the oxygen reacts with any rust, leaving away a solid piece of metal.
Kaseki and Chrome think this will be easy, until it's pointed out that the glass container would melt into goo at that temperature, so they need to find a way to heat only the tungsten paste to that temperature, and this will be a task they'll do without Senku's help to split the work.
Chrome realizing that Senku has trusted him to work this out using his own knowledge, feels very accomplished and excited. He does a high five with Senku as they officially split the tasks.
Kaseki, whom was watching from the top of the furnace, says he's envious of them. Since he was a boy, he always loved crafting things, but people only exploited this by having him craft things for them, never having anyone to actually share this interest and excitement with. He laments about this, wishing he could have a maker buddy or two. Chrome corrects him pointing out that he does have two makes buddies, Senku and him, and that the age difference they have doesn't matter really. Kaseki is overjoyed to tears by this and gets completely inspired to work on the task, bursting his clothes as usual.
With the heating team going on their work, Senku grabs Gen and drags him to the lab (literally). He brings up a lengthy method to refine the Calcium Tungstate ore into pure tungsten trioxide, remarking that Gen probably won't get any of it, and indeed he doesn't.
The heating team of Chrome and Kaseki begins playing with ideas for their task, with Kohaku and Magma watching close by. Chrome suggest using a large lens to focus sunlight, bringing Magma bad memories of the grand bout. In order to assess the obtained temperature, they set samples of various metals inside the glass vessel with increasing melting points, Lead, Silver, Gold and Iron.
The weak sunlight of winter does litte to nothing, even to the lead sample, so Chrome decides to complement it by setting the glass container on the stove from the cotton candy machine. The sunlight and the stove, with Suika and Chrome operating the bellows managed to melt the lead. Switching themselves for Kinro and Ginro at the bellows melted silver and gold, and increasing the power further to Magma and Kohaku melted the iron.
Chrome refused to stop there however, even though they went right past the 1000 degree goal, as Senku said the hotter the better. Chrome brings forth a large battery and starts experimenting with also incorporating electric heating through the night.
The morning after, the visibly sleep deprived Senku and Gen have finished the tungsten oxide paste, and they meet with Chrome who's done working out the heater setup. Senku finds it very inelegant, but then remarks that it might give the best result despite beign cumbersome.
So they finally can join everything together. Kohaku and Magma put their best into the bellows, as Kaseki manipulates the lens and Senku watches the electrolyzer that produces hydrogen gas. All their added efforts came together to craft the tiny but powerful tungsten filament, made of the world's most heat resistant metal, and the heart of the cellphone.
Characters in Order of Appearance
Chapter notes
- The Kingdom of Science has gathered a big stash of scheelite ore, they can now continue making the cellphone.
- Magma's attitude towards work has changed since getting trapped in the cave with Senku.
- Chrome is thrilled to be entrusted with doing a task on his own using his own ingenuity.
- Kaseki is happy to realize Chrome and Senku are the maker buddies he wanted to have all his life.
- The kingdom of science succeeds in making a tungsten filament.
- Scheelite is a mineral of calcium tungstate and fluoresces blue under the UV light rays of dawn.
- Scheelite is processed into a powder of tungsten trioxide which is mixed with honey into a paste, then extruded into a thin noodle of sorts, which is then treated with hydrogen at a high temperature to reduce the oxide into tungsten metal.
- The calcium tungstate is first reacted with sodium hydroxide and then calcium chloride which turns it back into calcium tungstate but in a pure crystallized form. Then it goes through two cycles of reacting first with hydrochloric acid and then ammonia, yielding tungsten trioxide.
- The hydrogen gas is made by passing electricity through water.
- The pinpoint heating device invented by Chrome combines heat from a charcoal stove with bellows, concentrated sunlight and a resistive electric heater.
- Scheelite is processed into a powder of tungsten trioxide which is mixed with honey into a paste, then extruded into a thin noodle of sorts, which is then treated with hydrogen at a high temperature to reduce the oxide into tungsten metal.
- The melting points of various materials:
- Tungsten 3400°C
- Rhenium 3100°C
- Osmium 3000°C
- Iron 1500°C
- Gold 1100°C
- Silver 1000°C
- Glass 700°C
- Lead 350°C
